Samira Sadeghi
email: samira.sadeghi-8@etudiants.ensam.eu

Mohsen Sadeghi
email: mohsen.sadeghi@proctonlabs.org

Ali Siadat
email: ali.siadat@ensam.eu

Patrick Martin
email: patrick.martin@ensam.eu

William Ziz
email: william.ziz@proctonlabs.org

Intelligent feature based resource selection and process planning

Keywords: Process planning, STEP, Knowledge based, integrated design, manufacturing

This paper presents an intelligent knowledge-based integrated manufacturing system using the STEP feature-based modeling and rule based intelligent techniques to generate suitable process plans for prismatic parts. The system carries out several stages of process planning, such as identification of the pairs of feature/tool that satisfy the required conditions, generation of the possible process plans from identified tools/machine pairs, and selection of the most interesting process plans considering the economical or timing indicators. The suitable processes plans are selected according to the acceptable range of quality, time and cost factors. Each process plan is represented in the tree format by the information items corresponding to their CNC Machine, required tools characteristics, times (machining, setup, preparatory) and the required machining sequences. The process simulation module is provided to demonstrate the different sequences of machining. After selection of suitable process plan, the G-code language used by CNC machines is generated automatically. This approach is validated through a case.

Introduction

Integrated manufacturing modelling is the main subject of manufacturing environment design and computerized manufacturing support systems [START_REF] Zdrahal | Selecting Manufacturing Technology: A Knowledge Modelling Approach[END_REF], [START_REF] Lee | Eliciting information for product modeling using process modeling[END_REF]. Principal activities involved in the integrated manufacturing include product design, process design, suitable manufacturing process selection and planning [START_REF] Tichkiewitch | Integration of Manufacturing Processes in Design[END_REF].

The selection of a suitable machining process for a given set of product characteristics and requirements is one of the most significant and important issues in product development. The early process selection combined with product-process compatibility analysis determines various parameters to integrate the diverse constraints imposed by different experts. This analysis is first and foremost based on the experimental knowledge of the experts. One of the important aspects of knowledge based integrated manufacturing design systems is the development of an adequate solution for representing and correlating different types of knowledge. The expert knowledge modeling facilitates the understanding of the complex interrelationships within integrated product-process model in product development.

The link between the product, its associated process and resource plan belongs to knowledge formalization. Experts use their knowledge to determine the selection of the manufacturing processes and associated resources or to define the product parameters considering the manufacturing and resources constraints.

Effective process selection for a given set of product characteristics & requirements is a multi-criterion problem which is strongly influenced by interdependent manufacturing knowledge like product knowledge (product complexity, design requirements, product quality) and resource knowledge (resource availability, characteristic and cost). Based on the information provided regarding the role and experiences of experts in product-process design this knowledge is formalized. The process-resource selection involves two steps: step 1 involves the evaluation of available processes for their technical capability in order to appropriately respond to design requirements and step 2 ranks the process performance with regard to its resource consumption economically [START_REF] Esawi | Cost-based ranking for manufacturing process selection[END_REF]. Many methods have been proposed to support these steps. Ashby [START_REF] Ashby | Selection strategies for materials and processes[END_REF] proposes the selection of manufacturing processes considering their compatibility with the geometrical parameter and the resources needed followed by ranking of the relative costs associated. The final choice is performed with respect to the rating, industrial knowledge, and available manufacturing resources; however, the approach adopted in this research does not target a specific manufacturing domain.

To determine the sequences of specific manufacturing process, Lovatt [START_REF] Lovatt | Manufacturing process selection in engineering design[END_REF] describes the framework based on the definition of process plan with different manufacturing tasks (steel cutting, steel heat treatment, casting, etc). The process selection is carried out by the combination of manufacturing process attributes, material parameters, and product specifications to satisfy design requirements [START_REF] Zha | A web-based advisory system for process and material selection in concurrent product design for a manufacturing environment[END_REF]. The approach proposed by Gupta [START_REF] Gupta | Activity based costing and management and its implications on operations management[END_REF] consists of three phases: (1) identification of the pairs of material/process that satisfy the required conditions (economical and geometrical specifications), (2) generation of the possible process plans from identified material/process pairs, and (3) selection of the most interesting process plans considering the economical indicators. In Ishii's work [START_REF] Ishii | Methods for process selection in design[END_REF], [START_REF] Ishii | HyperQ/Process -An Expert System for Manufacturing Process Selection[END_REF], the process selection is decomposed into two steps: (1) the first step is the identification of relevant parameters that affect manufacturing processes selection and (2) the second step consists in developing the representation schemas for knowledge used during the manufacturing processes selection. This knowledge is used to determine compatibility between product specifications and process parameters in order to rank the possible manufacturing processes according to the performance of economical indicators more precisely. Boothroyd [START_REF] Boothroyd | Production Design for Manufacture and Assembly[END_REF] propose the selection of the material/process pairs based on the process capability in terms of geometrical specifications realization and material constraint. The final selection is determined by the elimination of the unacceptable material/process pairs, considering the related constraints and predefined indicators, such as the cost.

In terms of integrated manufacturing systems, the feature-based approaches have been recognized as essential tools to integrate design and automated process planning. In this context, Devireddy [START_REF] Devireddy | Feature-based modeling and neural networks-based CAPP for integrated manufacturing[END_REF] presented a methodology of integrating the design and planning of manufacturing by utilizing the concept of feature-based modeling. Khoshnevis [13] described architecture of an integrated process planning system, called 3I-PP, which is comprised of three modules: feature completion, process selection, and process sequencing. Berger [START_REF] Berger | A Heuristic STEP-NC Based Process Planning Tool for Sequencing NC Machining Operations[END_REF] presents an approach for enabling the automatic preparation of STEP-NC based Workplans with methods known from graph theory. Based on that, it is possible to use algorithms to find the shortest path inside this directed graph as optimal sequenced solution under given requirements. Finally, the corresponding NC machining code will be generated and distributed to the machinery.

The research results presented in this paper contributes to knowledge-based integrated manufacturing support by development of a computerized system to process planning, utilizing the concepts of STEP feature-based modeling and rule based intelligent techniques. The suitable processes plans are selected according to the acceptable range of quality, time and cost factors. This approach is validated through a PPRint (Product, Process, Resource integrating) tool development and the application of a case study.

Table 1, summarizes the characteristics of different manufacturing process selection approaches.

Knowledge within Process Planning

Integrated manufacturing is considered as a network of product, process and resource parameters and expert's knowledge as a set of constraints [START_REF] Ly | Integration and verification of semantic constraints in adaptive process management systems[END_REF] applied on the parametric network. In engineering, constraints are formalized as: special design requirements that must be satisfied; logic reasoning activity of experts; dependency between design functional requirements, design parameters and flow of information between experts to support interdisciplinary knowledge integration (figure 1-a).

Figure 1 constraint classification in the process planning

The design and related constraint representation provides an integrated productprocess decision making approach to evaluate its consistency and is useful in selecting a suitable manufacturing process and product design parameters [START_REF] Thibault | Proposal for Product Process Integration using Classification and Rules[END_REF] (figure 1-c). Our main objectives are:

To provide an effective data representation model supporting the integration of different elements (product, processes, and resources) and analysis of relationships and related knowledge between them Gather and integrate knowledge related to the product definition and the manufacturing process to control the whole production process, allowing us to produce a better product Improving the exploitation of knowledge capital in new projects Provide a basis for knowledge capitalization and reuse issued from different product development projects So, constraint definition and classification are the key issues for this framework. We need to consider practical ways to represent design constraint in process planning environment.

Constraints in a process planning analysis can be simply classified into constraints inside each kind of entity model and constraints between different kinds of entity models according to the product, process and resources view [START_REF] Sadeghi | Toward a framework for effective collaborative product development[END_REF] (figure 1-b):

Product: Product constraint that represents relationships between entities defined by product model, for example, constraints about dimension, geometry, tolerance, features, etc. Process: Process constraint that represents relationships between entities defined by process model. For example, the dependency constraint between two sequences of machining operation Resources: Resources constraint that represent relationships between entities defined by resource model. For example, availability, compatibility Product/process constraint: such as constraint about product features property and process parameters to realized this features Process/Resources constraint: for example, constraint about choice of tools for machining specific feature according to optimum manner, feature property, quality, cost and machining time Product/ Resources constraint: for example the constraint about product property and resource characteristic (Product features vs. Machine accessibility) The manufacturing process selection combined with product-process-resource compatibility analysis to determine the various parameters and steps as well as the correlation of requirement. The purpose is to find a path among several process planning obstacles that could lead to a better solution that satisfies the diverse requirement considering constraints imposed by different experts throughout the process planning. In manufacturing industries, this analysis is first and foremost based on the experimental knowledge of the experts.

The method we describe in this paper is based on the declaration and checking of expert's knowledge (constraint) in order to check the coherency between product, process and resource elements.

With the definition of constraint categories, the system provides the suitable constraint verification. It allows specifying which constraint representation approach is possible for each element of data model.

We consider following general steps which must be considered to cerate a suitable process plan (figure 2):

1. The step provides the environment to import the STEP file and to illustrate the product information which is necessary to analyze the coherent manufacturing process. It contains product constraint which defines the relationship between the elements of product in STEP standard. 2. The step determines optimum procedure for machining each feature according to feature characteristic, part material, tool life, available tool in data base and other constraint. 3. The step generate micro process planning according to optimum procedure for machining each feature, spindle speed and feed rate, possible tool direction and orientation for machining and other constraint. 4. The step generate macro process by considering the information about precedence machining feature, setup face, machining face, setup time, time of tool moving between each feature and time of tool changing. 5. The step presents the selection of coherent CNC machines and the optimum sequences of machining for each CNC machine. The features characteristic and the tool accessibility knowledge are the necessary elements to select the CNC machine. 6. The step presents the cost model for manufacturing process. It contains different costs for different process attributes: physical attributes such as the materials, the tolerance, size range, time, complexity of shape; and economic attributes such as tooling cost, and rate of production. This module is used to select the acceptable process identifying the cost value specified by the cost model. The effect is to eliminate the processes which cannot meet the specifications. The estimated cost and the time required for the selected process are displayed in the process plan, which is the output of this module. 7. The step is used to prepare the manufacturing process by generating the corresponding G-code for the CNC machine. To generate G-code, this module gets the process plans information as input 8. The step is used to simulate the machining sequences (process plan). Each step of simulation demonstrates the machining direction and the tool required to realize the feature. The aim of the proposed approach is facilitated process planning, design and manufacturing integration and decrease human error in other words allow expressing all technical and non-technical constraints through all life cycle phases of an integrated manufacturing.

The application protocol implemented in this research work is based on STEP AP224 which contains explicit high-level part data in terms of feature attributes, tolerances, material specifications. It can be used to represent the information needed to define product data necessary for manufacturing product. The proposed system consists of the STEP-based feature modeler and intelligent process planning. The figure 3 gives an example of architecture to realize the process plan (the Holes analysis is represented as an example). The first step of the system uses STEP features as the basic elements for product representation and generates the graphical STEP AP224 based product representation. The product characteristics and the features parameters are represented in tree view and graphical format by the feature modeler. This modeler uses the specific algorithm to convert product information (STEP AP224) into a tree based representation format to be used as input for process planning. Figure 4 shows an example of feature based representation of product in the system.

This representation provides the part information to execute the following steps: micro process planning to determine the machining procedure for each feature according to machining parameters and tools selection selection of suitable CNC machine macro process planning to generate the process plans generation of G-codes of process plans and simulation possibility

micro process planning to determine the machining procedure for each feature and parameters and tools selection

This step selects the machine tools on which the machining operations can be performed to produce the given feature. This step is implemented using a product information, tools data base, tools knowledge as input of the step. Figure 6 presents the user interface to edit the tool databases. Experts use this interface to complete the database according to available tool information. This step receives information for each feature in the part and generates the needed machining operations to realize the feature. The knowledge of tools accessibility for machining feature and tool databases are the main inputs of this step. The outputs of this step are: 1) the direction of tool for machining feature, 2) the procedure of machining feature for rough and finishing, 3) the feed rate and spindle speed, 4) the machining time, 5) the tool cost.

The tools selection is based upon machining feature and its associated machining operation. The output of this step contains recommended tools to be used to realize the feature. These recommended tools can be used as keys to search available tool databases to find the suitable tool.

selection of suitable CNC machine

The CNC machine selection is realized by considering some constraints about feature orientation and feature position data of each feature which are provided from: 1) design file, 2) knowledge of tool direction accessibility for machining of each feature and 3) knowledge of accessibility of each type of CNC machine to part. According to these constraints and constraints related to part dimension, part weight vs. max table load of CNC machine, the suitable CNC machine is selected from the available CNC machines database. Figure 5 shows the user interface to manipulate the CNC machine database.

macro process planning to generate the process plans

The process plan generation is a procedure to group the sequence of machining features into process plan. The operation sequence arranges the machining sequences in each generated process plan by considering the information about precedence machining feature, setup face, machining face, setup time, time of tool moving between each feature and time of tool changing. In addition, the optimization algorithms are implemented to select the optimal process according to manufacturing process cost, setup time, tool changes time among the operations. The system contains a set of rules guiding the process planning selection for prismatic parts.

As shown in Figure 7, the alternative process plans are proposed for related part. Each alternative process plan indicates the selected CNC machine and the sequences of machining to be executed during setup. The machining features describe what the machine should do and the machining sequences describe how the features should be manufactured with related sequence tool. The cost presentation allows combination of several cost produced during process plan setup such as material, tools, CNC machine and labor cost to estimate final manufacturing cost. The tool and machine information are also provided to give the details of tools and machine used during machining sequences.

generation of G-codes of process plans and simulation possibility

As shown in Figure 8, the specific facility is provided to generate a G-code of physical process plan. This step receives the information related to the part (features, material, etc.) and information produced by process planning (machining operations, tools, process sequences parameters, etc.) to generate a G-code file. Specific module is developed to use the provided information to simulate the machining sequences in the 3D format.

Conclusion

Intelligent manufacturing process selection improves the efficiency of manufacturing process. In PPRint tool, in the product design stage, the product model is based on the STEP application protocol, AP 224. A STEP-based feature modeler has been developed to browse the STEP file and to illustrate the product information in the feature tree view and in the graphical format. In process planning stage, an intelligent rule based process planning system has been developed to integrate the manufacturing process attributes, material parameters, and product specifications to satisfy design requirements.

The approach proposed, consists of different phases, such as identification of the pairs of feature/tool that satisfy the required conditions according to optimum procedure (example: the suitable depth of cut, spindle speed and feed rate that will be chosen during machining.), generation of the possible process plans from identified tools/Machine pairs, and selection of the most interesting process plans considering the economical or timing indicators (Example: cost of material, cost of machine, cost of tool, setup time, machining time, tool change time). The suitable manufacturing processes plans are selected according to the acceptable range of quality, time and cost factors. Each process plan is represented in the tree view format by the information items corresponding to their CNC Machine, required tools characteristics (characteristic, cost), times (machining, setup, preparatory) and the required machining sequences. The process simulation module is provided to demonstrate the different sequences of machining to realize the final piece. After selection of suitable machining sequences, the G-code language used by CNC machines is generated automatically.

In PPRint, the AP224-STEP (machining feature) is used as input, in other words according to feature based design this format is provided to process planning, but it's not possible to force designer to design in feature base procedure. In this situation feature extraction is inevitable to capture features parameters for process planning.

Figure 2

 2 Figure 2 The manufacturing process and resource selection process

Figure 3 Figure 4

 34 Figure 3 system architecture

Figure 5 Figure 6

 56 Figure 5 user interface of tool database

Figure 7

 7 Figure 7 the process plan information detail

Figure 8

 8 Figure 8 the G-code generation and machining sequences simulation facility

Table 1

 1 Comparison of the approaches "manufacturing processes selection"

	Approach	Choice of	Choice of	Associated	Economical
		manufacturing	material	tool	evaluation
		process
	Ishii	Yes	No	HyperQ	Yes
	Ashby	Yes	Yes	CES	n.a.
	Gupta	Yes	Yes	Seer-DFM	Yes
	Boothroyd	Yes	Yes	DFMA	Yes
	Lovatt	Yes	n.a.	n.a.	Yes
	Devireddy	Yes	No	n.a.	n.a.
	Khoshnevis	Yes	Yes	3I-PP	Yes
	Berger	Yes	No	n.a.	n.a.
	Sadeghi	Yes	Yes	PPRint	Yes

Description of the proposed process selection approach

This work focuses on developing a feature-based intelligent process planning. The main purposes of the intelligent process planning are: (1) to integrate a standardized featurebased STEP model with process planning utilizing, and (2) developing a knowledge based and rule-based techniques, and (3) to generate a G-code process plan containing all the information to setup a CNC machine .


Mohannad Ismail

Joan Van Baaren

Valérie Briand

Jean-Sébastien Pierre

Philippe Vernon

Thierry Hance

Fitness consequences of low temperature storage of Aphidius ervi

Keywords: Aphidius ervi, low temperature exposure, cumulative fecundity, intrinsic rate of

In biological control programs, storage at low temperatures is used to produce large number of individuals before inundative releases. However, an exposure to low temperatures may affect the survival of exposed individuals and some life history traits such as the daily fecundity or the longevity of the survivors. This impact on life history traits is important because they will determine the growth potential of the population. To estimate the costs of different treatments of low temperature exposure, we analyzed the main instantaneous demographic parameters of the parental generation of Aphidius ervi Haliday (Hymenoptera: Braconidae) when exposed to three storage temperatures (7, 4 and 0°C), combined with two storage durations (1 and 2 weeks) and two thermal regimes (constant and fluctuating), which represents a total of 12 treatments and a control.

The average cohort generation time (Tc) decreased significantly after exposure to low temperature, particularly in fluctuating treatments. This means that development continues during storage. Cumulative fecundity and the net reproductive rate (R 0 ) decreased significantly for most of the storage treatments. This decrease was most pronounced in the constant temperature treatments. Females under fluctuating thermal regime produced a higher cumulative fecundity than those exposed to constant temperatures. Surprisingly, an exposure to 0°C over one week did not affect emergence rate and fecundity whereas all other treatments did.

Storage at low temperatures may affect the efficiency of inundative releases, with the exception of storage for one week at 0°C. Moreover, cumulative fecundity and net reproductive rate (R 0 ) represent a more immediate prediction of the increase of the population after low temperature exposure than the intrinsic rate of increase (r m ), and reflect the qualities required in an inundative release context.

increase, net reproductive rate, sex-ratio, trade-off.

Introduction

Demographic studies of population size and density, age distribution, and pattern of growth can be used to elucidate biological traits such as genetic structure, behaviour and ecology, which is necessary to predict the growth or decline of a population [START_REF] Andrewartha | The Distribution and Abundance of Animals[END_REF][START_REF] Chi | Life-table analysis incorporating both sexes and variable development rates among individuals[END_REF][START_REF] Price | Insect Ecology: Behavior, Populations and Communities[END_REF]. These studies are important tools that provide comprehensive data on the survival, development time, longevity of adults, and the reproduction capabilities of each female [START_REF] Yang | Life tables and development of Bemisia argentifolii (Homoptera : Aleyrodidae) at different temperatures[END_REF][START_REF] Yu | Comparison of the life tables and predation rates of Harmonia dimidiata (F.) (Coleoptera: Coccinellidae) fed on Aphis gossypii Glover (Hemiptera[END_REF]. Demographic analysis of various life history parameters has been applied on a variety of organisms including a large number of insect species (e.g. [START_REF] Blanco | Soybean flour and wheat germ proportions in artificial diet and their effect on the growth rates of the tobacco budworm, Heliothis virescens[END_REF][START_REF] Chi | Life-table analysis incorporating both sexes and variable development rates among individuals[END_REF][START_REF] Yang | Life tables and development of Bemisia argentifolii (Homoptera : Aleyrodidae) at different temperatures[END_REF]) and the natural enemies of agricultural pests [START_REF] Amir-Maafi | Demography of Habrobracon hebetor (Hymenoptera: Braconidae) on two pyralid hosts (Lepidoptera: Pyralidae)[END_REF][START_REF] Atlihan | Temperature-dependent development and demography of Scymnus subvillosus (Coleoptera: Coccinellidae) reared on Hyalopterus pruni (Homoptera: Aphididae)[END_REF][START_REF] Chi | Age-stage, two-sex life tables of Aphidius gifuensis (Ashmead) (Hymenoptera: Braconidae) and its host Myzus persicae (Sulzer) (Homoptera: Aphididae) with mathematical proof of the relationship between female fecundity and the net reproductive rate[END_REF][START_REF] Nunez-Campero | Survival analysis and demographic parameters of the pupal parasitoid Coptera haywardi (Hymenoptera: Diapriidae), reared on Anastrepha fraterculus (Diptera: Tephritidae)[END_REF]. They allow growth predictions based on population models to be developed [START_REF] Carey | Applied Demography for Biologists with Special Emphasis on Insects[END_REF] and may help to forecast both the effectiveness of a parasitoid in the field [START_REF] Ehler | Introduction strategies in biological control of insects[END_REF]) and its interactions with insect pests and competitors of natural enemies [START_REF] Omer | Demography of the leafminer parasitoid Ganaspidium utilis Beardsley (Hymenoptera: Eucoilidae) at different temperatures[END_REF][START_REF] Roy | Effect of temperature on intrinsic rates of natural increase (rm) of a coccinellid and its spider mite prey[END_REF].

Temperature is one of the most important climatic conditions affecting survival, development, phenology, reproduction, sex-ratio, dispersal, population growth and thus abundance [START_REF] Amiri | Effect of temperature on demographic parameters of the hawthorn red midget moth, Phyllonorycter corylifoliella, on apple[END_REF][START_REF] Angilletta | Thermal Adaptation: A Theoretical and Empirical Synthesis[END_REF][START_REF] Hance | Impact of extreme temperatures on parasitoids in a climate change perspective[END_REF][START_REF] Omer | Demography of the leafminer parasitoid Ganaspidium utilis Beardsley (Hymenoptera: Eucoilidae) at different temperatures[END_REF]. Several papers described the effect of high and low temperatures on insect life history traits (e.g. [START_REF] Ismail | Physiological costs of cold exposure on the parasitoid Aphidius ervi, without selection pressure and under constant or fluctuating temperatures[END_REF][START_REF] Mawela | Effect of temperature and host species on parasitism, development time and sex ratio of the egg parasitoid Trichogrammatoidea lutea Girault (Hymenoptera: Trichogrammatidae)[END_REF][START_REF] Moiroux | Local adaptation of a Drosophila parasitoid: habitat-specific differences in thermal reaction norms[END_REF]. Low temperatures were used in the field of biological control in order to produce simultaneously a large amount of natural enemies, available when they are necessary [START_REF] Bueno | The effect of temperature and host density on the reproduction of Aphelinus perpallidus (Hymenoptera: Aphelinidae)[END_REF]. There are however few studies that investigate the consequences of exposure of specific developmental stages to low temperatures and the impact this exposure could have on the phenotypic plasticity of the individual traits that determines the growth of populations [START_REF] Chen | Maternal and progeny quality of Habrobracon hebetor Say (Hymenoptera: Braconidae) after cold storage[END_REF]Chen et al. 2008a;Chen et al. 2008b). Such exposure is regularly practiced in mass rearing of insects used in biological control [START_REF] Leopold | Post pupariation cold storage of three species of flies: Increasing chilling tolerance by acclimation and recurrent recovery periods[END_REF]. Under these conditions, cumulative damages due to storage can occur and the expression of fitness traits can be effected (see [START_REF] Colinet | Insect parasitoids cold storage: A comprehensive review of factors of variability and consequences[END_REF] for a review). However, most of the publications examining the effects of storage at low temperatures evaluate some specific fitness traits [START_REF] Van Baaren | Effect of low temperature exposure on oviposition behaviour and patch exploitation strategy in parasitic wasps[END_REF], without evaluating the overall consequences for the population. From an agronomic point of view, the question is: how to evaluate the number of reproductive females that can be produced by a generation of stored individuals? Several indicators can be used, such as the net reproductive rate (R 0 ) and the intrinsic rate of increase (r m ) calculated on the basis of survival, fertility, development time and sex-ratio of offspring [START_REF] Andrewartha | The Distribution and Abundance of Animals[END_REF][START_REF] Carey | Applied Demography for Biologists with Special Emphasis on Insects[END_REF][START_REF] Nunez-Campero | Survival analysis and demographic parameters of the pupal parasitoid Coptera haywardi (Hymenoptera: Diapriidae), reared on Anastrepha fraterculus (Diptera: Tephritidae)[END_REF], as well as the cumulative fecundity [START_REF] Chen | Maternal and progeny quality of Habrobracon hebetor Say (Hymenoptera: Braconidae) after cold storage[END_REF][START_REF] Hance | Selection of Azolla forms resistant to the water lily aphid, Rhopalosiphum nymphaeae -Susceptibility of Azolla forms to Rhopalosiphum nymphaeae[END_REF][START_REF] Kennedy | Demecology of the false spider mite, Brevipalpus phoenicis (Geijskes) (Acari, Tenuipalpidae)[END_REF]. The novelty of our study was to compare the different parameters representing the population growth rate.

In this framework, our goal was to analyse the effect of low temperature exposure on the parasitoid Aphidius ervi (Haliday) (Hymenoptera: Braconidae) for one and two week periods when still inside its host at the mummy stage. We chose three temperatures above and below the development threshold (T 0 = 6.6°C) [START_REF] Sigsgaard | The temperature-dependent duration of development and parasitism of three cereal aphid parasitoids, Aphidius ervi, A. rhopalosiphi, and Praon volucre[END_REF]. Our assumptions are: 1) demographic parameters will be affected by low temperatures and exposure time, 2) the development of the mummy is expected to continue at the temperature above T 0 and thus the emergence after exposition should be faster than temperatures that are below T 0 . 3) Previous studies have shown that fluctuating temperatures are less stressful than the constant ones, when the effect of low temperature storage was measured on different life-history traits [START_REF] Colinet | The impact of fluctuating thermal regimes on the survival of a cold exposed parasitic wasp, Aphidius colemani[END_REF][START_REF] Ismail | Stress intensity and fitness in the parasitoid Aphidius ervi (Hymenoptera: Braconidae): temperature below the development threshold combined with a fluctuating thermal regime is a must[END_REF][START_REF] Ismail | Physiological costs of cold exposure on the parasitoid Aphidius ervi, without selection pressure and under constant or fluctuating temperatures[END_REF]. We predict that fluctuating temperatures will allow better resistance to exposure to low temperatures, and this should result in the demographic parameters being affected less than under constant temperatures. The purpose of this study was also to determine the best parameters to compare the effects of different treatments of storage on the growth rate of the generation exposed (i.e. the generation which will be released in the field).

Materials and methods

The parasitoid A. ervi was chosen as a model because it is commercially produced and widely distributed in several European countries for inundative releases [START_REF] Boivin | Aphid parasitoids in biological control[END_REF][START_REF] Stilmant | Host specialization in habitat specialists and generalists[END_REF]. The colonies of A. ervi and the grain aphid Sitobion avenae Fabricius (Homoptera: Aphididae) were maintained in the laboratory as described and explained in [START_REF] Ismail | Physiological costs of cold exposure on the parasitoid Aphidius ervi, without selection pressure and under constant or fluctuating temperatures[END_REF] and [START_REF] Ismail | What are the possible benefits of small size for energy-constrained ectotherms in cold stress conditions?[END_REF].

To determine the consequence of a low temperature exposure on the demographic parameters of A. ervi, we chose three temperatures: 7°C is just above the mummy-adult development threshold (T 0 = 6.6°C) for A. ervi [START_REF] Sigsgaard | The temperature-dependent duration of development and parasitism of three cereal aphid parasitoids, Aphidius ervi, A. rhopalosiphi, and Praon volucre[END_REF], 4°C is just below the (T 0 ) and 0°C above a potential freezing temperature. Two durations were used to store the mummies: 1 or 2 weeks, under two thermal regimes: constant storage temperature (C), or fluctuating storage temperature (F). For the fluctuating treatments a daily interruption of 2 hours at 20°C was practiced as described by [START_REF] Colinet | The impact of fluctuating thermal regimes on the survival of a cold exposed parasitic wasp, Aphidius colemani[END_REF].

One-day-old mummies of A. ervi were taken from the rearing colony three days per week and were randomly assigned to the control at 20°C or to one of the 12 storage treatments as described in Table 1. We used three identical incubators for the treatments (Sanyo MIR 153, Electric Co. Ltd, Japan) with a thermal precision of ± 1°C, under a photoperiod 16L: 8D, and humidity 60 ± 10%, and to avoid an incubator effect, a portion of the mummies of each treatment was exposed in each of the incubators.

For the 12 treatments, mummies were progressively acclimated by exposing them to 20°C and then reducing the temperature by steps over a 2 hour period (for 7°C: 2h at 17, 14 and 11°C; 4°C : 2h at 16, 12 and 8°C; 0°C : 2h at 15, 10 and 5°C) [START_REF] Levie | Consequences of acclimation on survival and reproductive capacities of cold-stored mummies of Aphidius rhopalosiphi (Hymenoptera: Aphidiinae)[END_REF]. After the exposure to low temperatures, mummies were transferred to 20°C using the opposite progressive temperature steps as for the low temperature exposure. In the control treatment and after each storage treatment, each mummy was individually placed in separate small gelatin capsules (Ø = 0.5 cm, L =1.5 cm). The following life history traits were measured after each storage treatment: Emergence rate Adult emergence rate was expressed as the percentage of individuals that emerged from control and stored mummies in each gelatin capsule. Emergence was recorded daily early in the morning.

Fecundity parameters

After emergence, one-day-old females were placed with one-day-old males from the same treatment in a Petri dish for 15 minutes, and they were observed until mating occurred. Females were then individually transferred to small caged pots containing a wheat plant with about 100 aphids of 3 rd and 4 th nymphal instars. The number of females used for each treatment is given in Tables 2 and3. This experiment was carried out at 20 ± 1°C with a 16L: 8D photoperiod. Since females usually lay their eggs at the beginning of their life, these pots were renewed every day during the five first days and then once every three days until the death of the female. The females were fed with honey ad libitum. Mortality of these females was checked daily from the first day of the experiment until their death. Daily fecundity was evaluated by counting the number of mummies obtained.

Demographic growth parameters of parental generation

The following parameters were measured in order to construct the life tables: development time (from oviposition to adult emergence), daily female fecundity (number of females produced per female) and female longevity. In the calculation of these parameters, the storage duration was subtracted from the total time spent under the mummy stage. Indeed, for practical purposes, the most important feature for control of the agronomic pest is the time needed for adults to emerge after the storage. However, in this case, development time for individuals exposed to temperatures above the (T 0 ) or under fluctuating regimes was probably underestimated as development was still possible at that temperature.

The intrinsic rate of increase (r m ) was determined by solving numerically the Birth's approximation of Lotka's equation [START_REF] Birch | The intrinsic rate of natural increase of an insect population[END_REF][START_REF] Carey | Applied Demography for Biologists with Special Emphasis on Insects[END_REF]: ∑ l x . m x .e -rx = 1, where x is the age class, l x the probability of survival till class x, and m x the fecundity of the class x. The generation time (Tc) was calculated as the mean interval separating the birth of one generation from the birth of the next one, as: Tc = ∑ (l x .m x .x)/ ∑ l x .m x . The net reproductive rate (R 0 ), represented the mean number of female offspring produced by each female during its entire life [START_REF] Birch | The intrinsic rate of natural increase of an insect population[END_REF][START_REF] Carey | Applied Demography for Biologists with Special Emphasis on Insects[END_REF], and was calculated as: R 0 = ∑ l x .m x .

We used the jackknife technique to estimate the mean demographic parameters and the standard errors (SE) of the demographic parameters of the life table as previously used by [START_REF] Meyer | Estimating uncertainty in population growth rates -jackknife vs bootstrap techniques[END_REF] and Chen et al. (2008a, b). The Jackknife analysis method removes one observation at a time from the original data set and recalculates the statistic of interest from the truncated data set as follow: ř i = n • r all -(n-1) • r i , where n is the number of females, r all is the pseudovalue for all females and r i is the pseudovalue for each female individual in turn. These values are referred to as pseudovalue [START_REF] Efron | Overdispersion estimated based on the method of of asymmetric maximum likelihood[END_REF]. The values of r m per female and per temperature were calculated by using the software Microsoft Excel and its numerical solver. The method can estimate Tc, R 0 and r m with their respective jackknife variances.

Progeny sex-ratio

The mummies of the F1 generation were placed in a plastic Petri dish until emergence in order to determine the sex-ratio of the progeny (the number of females divided by the number of males).

Statistical analyses

The emergence rates were compared between treatments using a χ² test. Curves of cumulative fecundities were calculated according to the model of Von Bertalanffy in weight (VBM, Von Bertalanffy, 1934)

: Y = K*(1-exp (-a*x)) ^3
, where Y represents the value of the cumulative fecundity at age x, K is the maximum number of offspring per female (plateau value), and a is the parameter which governs the inflection point (log(3)/a). Von Bertalanffy's model in weight is suitable for representing the evolution of mass of a growing organism or of a part of it.

VBM were fitted by non-linear least squares (nls function in R) and compared through their two parameters a and K, whose standard error estimators are provided. An overall F test in R language was written, for a given parameter subject to one or several factors, and then applied to Bonferroni's test in order to compare the parameters two by two. As the control level has a single modality for the duration of storage and for the thermal regime, the duration of storage and the temperature of storage is to be considered as nested inside the thermal regime (nesting factor with three levels: control, constant temperature, fluctuating temperature), as well as their interaction.

Tc, considered as a time delay, was analyzed by Cox Proportional Hazard Model including temperature, storage duration and thermal regime as fixed factors. R 0 and r m were analyzed by Generalized Linear models with the Gaussian family, equivalent to classical analysis of variance, including temperature, storage duration and thermal regime as fixed factors. Progeny sex-ratio was analyzed by Generalized Linear models, including temperature, storage duration and thermal regime as fixed factors. Sex-ratio was considered as a binomial variable and thus under the logistic family with logit link. When there were interactions among the factors, we considered all combinations of storage temperature and storage duration in pairwise comparisons and each against the control. The total is therefore 13 x 6 = 78 comparisons. For R 0 , a Tukey Honest Significant Difference test was used because there is an appropriate compromise between power and conservativeness in this test. For the other parameters, Bonferroni's post hoc multiple comparison tests were used (α = 0.05 k -1 , where k is the number of comparisons, here 78). Data are presented as means (± SE). Statistical analyses were done using the statistical package R version 2.8.0 (R Development Core Team, 2008).

Results

Emergence rate

The emergence rate of A. ervi varied from 80 to 95 % under the low temperature treatments and reached 97 % in the control (Table1). The lowest value (80 %) was obtained under constant exposure over two weeks at 0°C (0C2). However, no statistical difference was recorded among the 13 treatments (χ² 12 = 3.10, p = 0.995).

Cumulative fecundity of parental generation

The analysis of cumulative fecundity using the model of Von Bertalanffy comparing the sigmoid curves presented significant differences among treatments (F 24, 1302 = 82.20, p < 0.001). Only females exposed at 0°C for one week duration of storage (0C1: K = 54.66 and a = 2.50 days with progeny sex-ratio: 0.57 females) showed a comparable value to the control (K = 52.88 and a = 2.72 days with progeny sex-ratio: 0.57 females) (Table 2). All tested females produced offspring after the storage at low temperatures except a single female in treatment 4C2. The inflection point (a) of the fecundity curves indicates that the peak of fecundity is much earlier in the 4C2 and 0F1 treatments (1.82 days and 1.86 respectively) illustrating a more rapid population growth than in the control (2.72 days) or the treatment 0F2 (3.41 days) but this is compensated by a reduced total fecundity (K value).

Demographic growth parameters of parental generation

The significant differences in demographic parameters of A. ervi for the different treatments are presented in Table 3. The generation time (Tc) decreased significantly under storage temperatures at 7 and 4°C compared to the control (Cox proportional hasard model: χ 2 4 = 215.55, p < 0.001) and according to both durations of storage (χ 2 2 = 23.57, p < 0.001). It was also shorter under the fluctuating regime (χ 2 2 = 58.60, p < 0.001). There was a significant three-way interaction among the three tested factors (χ 2 27 = 165.43, p < 0.001). However, the interaction was weak and indicated a reduction of Tc for all modalities. However, the Tc of the fluctuating treatments decreased more sharply at 4°C than for the constant treatments. 2). The control was not significantly different from the 0C1, which provided the highest R 0, and both the control and the 0C1 were significantly higher than all the other treatments. In evaluating the effect of fluctuating regime relatively to the constant one, we found four cases weekly interacting, where the R 0 was higher in fluctuating regime than in constant regime (7C1-7F1, 7C2-7F2, 4C1-4F1 and 4C2-4F2), a case with no significant difference (0C2-0F2), and a case where fluctuating temperatures strongly depleted the R 0 (0C1-0F1). The reaction to storage temperature depends strongly of the combination of the temperature regime (fluctuating or constant) and storage duration. For one week storage at constant temperature, the R 0 decreased significantly from 0°C to 4°C and then increased slightly but significantly at 7°C. Conversely, under fluctuating regime, the R 0 was low at 0°C, remained steady at 4°C and increased strongly at 7°C. For two weeks storage under constant and fluctuating conditions, the R 0 was not significantly different at 0°C and 4°C but decreased strongly from 4°C to 7°C.

The intrinsic growth rate (r m ) only showed a slight effect of thermal regime (F 1, 118 = 4.16, p = 0.04) when the control level is dropped from the analysis. The r m did not vary significantly with the storage temperatures (F 4, 118 = 0.31, p = 0.87), nor with storage durations (F 2, 118 = 1.41, p = 0.25) (Table 2) and no interaction was found among these factors (F 4, 118 = 1.27, p = 0.29). The slight effect of thermal regime showed a better r m under fluctuating conditions than in constant ones. When all the levels are present, no significant effect on r m was detected indicating that r m was less sensitive to low temperatures, whatever the temperature and pattern of its management.

Progeny sex-ratio

The proportion of females in the F1 generation ranged from 0.42 to 0.55 at 7°C, from 0.40 to 0.51 at 4°C, and from 0.37 to 0.57 at 0°C. The nested analysis of deviance showed a significant effect of thermal regime ( 2 2 = 91.31, p < 0.001). The control, the treatment 0C1 and the fluctuating treatments displayed a higher female sex-ratio than all other storages at constant temperature. The factor temperature, nested in thermal regime was also significant ( 2 4 = 18.28, p < 0.001) whereas the factor storage duration was not ( 2 2 = 4.49, p = 0.11). The interaction temperature-storage duration, however, was highly significant ( 2 4 = 26.54, p < 0.001) indicating that the effect of temperature depends on storage duration. The two levels under fluctuating conditions showed an increasing sex-ratio from 0°C to 4°C and from 4°C to 7°C. Conversely, the patterns under constant temperature conditions differ in function of the storage duration. At 0°C, the female sex-ratio was high and not significantly different from the control. At 4°C the sexratio was very low, and at 7°C it was higher. In the opposite, after two weeks of storage, the females exhibited a very low female sex-ratio in their progeny at 0°C, and higher values at 4°C and 7°C. The difference 0C1-0C2 is large and significant, 4C1 and 4C2 do not differ significantly, neither do 4C1 and 7C1, nor 4C2 and 7C2. In summary, the fluctuating treatments induced a lower decrease in sex-ratio than the constant ones. The proportion of males also increased with the decrease in temperatures and the duration of cold exposure, with the exception of the 0C1 treatment which was the only one that do not differ significantly from the control.

Discussion

Effect of exposure to low temperature and duration on development time, emergence and fecundity Surprisingly, although demographic parameters were expected to be affected by low temperatures, the constant temperature treatment at 0°C over one week showed no significant difference to the control group at 20°C. The net reproductive rate (R 0 ) and the cumulative fecundity decreased significantly for all treatments except 0C1. Our hypothesis is that a temperature of 0°C over one week blocked the metabolic rate completely without any physiological damage or any increase in fat consumption which otherwise would have led to a reduction in fecundity. Interesting results were found after a constant and fluctuating exposure at 0°C for 4 weeks (see more in [START_REF] Ismail | Stress intensity and fitness in the parasitoid Aphidius ervi (Hymenoptera: Braconidae): temperature below the development threshold combined with a fluctuating thermal regime is a must[END_REF].

Our results showed that development continues in the constant treatments at 7°C and 4°C.

According to our prediction, 4°C is supposed to be below the T 0 , and so development should be stopped, but this was not the case, at least for our strain of A. ervi. Moreover, this T 0 value was estimated by [START_REF] Sigsgaard | The temperature-dependent duration of development and parasitism of three cereal aphid parasitoids, Aphidius ervi, A. rhopalosiphi, and Praon volucre[END_REF] using the "x-intercept" method [START_REF] Campbell | Temperature requirements of some aphids and their parasites[END_REF], which determined that the relation between y = development rate and x = the temperature is linear. This assumption might overestimate the T 0 , because this relationship is not linear for low temperatures [START_REF] Walgama | Evaluation of different models to describe egg and pupal development of Xyleborus fornicatus Eichh. (Coleoptera: Scolytidae), the shot-hole borer of tea in Sri Lanka[END_REF]. So, the development rate at low temperatures is not well known.

Similar results were obtained by [START_REF] Frère | Improvement in the cold storage of Aphidius ervi (Hymenoptera : Aphidiinae)[END_REF]. Whatever the temperature, the emergence rate after two weeks of exposure to low temperatures remains high and not significantly different from the control. This indicates that there are probably few lethal damages during that period, confirming previous results [START_REF] Ismail | What are the possible benefits of small size for energy-constrained ectotherms in cold stress conditions?[END_REF][START_REF] Ismail | Physiological costs of cold exposure on the parasitoid Aphidius ervi, without selection pressure and under constant or fluctuating temperatures[END_REF].

How to choose demographic indicators?

In the context of biological control, the choice of the most appropriate demographic parameters to assess the immediate impact of a release of parasitoids is of tremendous importance, particularly when an impact of storage on fitness traits is expected. The originality of this study is to compare the practical consequences of low temperature treatments on different demographic indicators.

For instance, only a few studies measured the demographic parameters after the storage. Chen et al. (2008a) used the R 0 to underline the decrease in population growth of the F1 generation of the parasitoid Gonatocerus ashmeadi after 20 days of adult storage at 10°C. Chen et al. (2008b) calculated r m and R 0 to present the decrease in population growth of the adult parasitoid G. ashmeadi, after they had been stored at immature stage for 30 days using a cycling fluctuating storage temperature regime under 4.5, 6 and 7.2°C but with no additional effect on the F1 generation. On the other hand, [START_REF] Chen | Maternal and progeny quality of Habrobracon hebetor Say (Hymenoptera: Braconidae) after cold storage[END_REF] used only the cumulative fecundity to present the decrease in population growth of the parasitoid Habrobracon hebetor after 10 days at 5°C of the parental storage.

The poor sensitivity of r m to low temperature storage might suggest that the population growth is not strongly affected by the storage, a point that was raised by [START_REF] Ismail | Stress intensity and fitness in the parasitoid Aphidius ervi (Hymenoptera: Braconidae): temperature below the development threshold combined with a fluctuating thermal regime is a must[END_REF]. This is not the case, because the use of r m parameters obtained for the prediction of the population growth, under stressful conditions, was only valuable if these conditions were continuously applied to subsequent generations. Moreover, the value of r m is indicative of the population growth only when the population had reached a stable age structure [START_REF] Carey | Applied Demography for Biologists with Special Emphasis on Insects[END_REF]) which is obviously not the case for a single stage mass release. R 0 is closer to the original definition of fitness by [START_REF] Haldane | The causes of evolution[END_REF]: the expectation of the number of viable and reproductive offspring.

Indeed, R 0 gives the total offspring expected to be produced by a female during its life. Thus R 0 represents a more immediate prediction of the increase of the population than r m , which is desirable for practical use in a biological control context. The cumulative fecundity curves correspond to the mean distribution of eggs a female can lay during its life. In particular the value of the inflection point (a) gives an accurate estimate of the moment of the peak of fecundity, which is an essential determinant of the intensity of the population growth. R 0 and the cumulative fecundity therefore reflect the potential of growth in an inundative release context better than r m .

For instance, it appears that the treatments (7C2, 4C1, 4C2, and 0F1) provoking the highest reduction in fecundity compared to control, also inflected at a younger age (Table 2). This earlier peak in fecundity is a compensatory effect on the rapidity of the population growth, and illustrates the probably a trade-off between the maximum number of eggs that can be laid daily and the precocity of the peak of fecundity. In consequence, the r m value of the 4C2 treatment remained similar to the control (0.239 and 0.232 respectively) whereas a reduction of 30 % in cumulative fecundity was observed (K value = 37.10 against 52.88 for the control). A simulation of population growth using the r m value under stress would therefore not make much sense. We suggest the use of the emergence rate, R 0 and the cumulative fecundity curves of first generation (including K and a parameters) to evaluate the immediate effects of the release of stored parasitoids in biological control. The R 0 and the cumulative fecundity and the inflection point may be considered as convenient proxies for immediate fitness [START_REF] Huey | Temperature, demography, and ectotherm fitness[END_REF].

Effect of fluctuating thermal regimes

Fluctuating regimes at the three temperatures (7, 4 and 0°C) still allow the development of the parasitoids inside the mummies as a clear reduction of development time once replaced at 20°C is observed in comparison to the control. This reduction may reach 4 days at 7°C. Furthermore, it appears that the fluctuating exposure alter the cumulative fecundity or the R 0 less than at constant exposure (except for the treatment 0C1 discussed above). It is known that the growth rate of insects can be affected by the daily fluctuations in temperature more than by the constant temperatures such as in the field environments [START_REF] Brakefield | Genotype-environment interactions for insect growth in constant and fluctuating temperature regimes[END_REF][START_REF] Brakefield | Matching field and laboratory environments -effects of neglecting daily temperature-variation on insect reaction normS[END_REF].

Practical applications in biological control

The values of Tc would give useful information concerning the expected time to adult emergence after exposure to low temperatures. In practice, for storage in case of mass release, a reduction of the development time of mummies complicates the distribution of mummies to farmers.

However, the knowledge of the relation between fluctuating temperature and reduction of development time will allow for the management of this difficulty by releasing individuals whose demographic capacities are less impaired than those under storage at constant temperature.

Moreover, this concern may be reduced if boxes where the mummies are kept are provided with honey during the delivery. This could even be an opportunity to obtain mating before release.

This is an important point for practical application.

In conclusion, an effective storage technique should result in a high emergence rates, and should no affect fecundity and reproductive activity [START_REF] Ismail | Physiological costs of cold exposure on the parasitoid Aphidius ervi, without selection pressure and under constant or fluctuating temperatures[END_REF][START_REF] Tauber | Prolonged storage of Chrysoperla carnea (Neuroptera: Chrysopidae)[END_REF]). In our case the best result was obtained at 0°C for 1 week and could be a suitable treatment to store the mummies of A. ervi without any deleterious effects on the growth rate for a short period. In the current study, observed mating and laying behaviour are very encouraging features for further commercial issues.

Table 1 : Summary of the 12 applied low temperature treatments and control, and the emergence rates ± SE (SE = √(pq/n) after each treatment.

 1

	Temperature	Duration	Regime	Treatment	Emergence rate %
	20°C	Until emergence	Constant	20C (115 mummies)	97.39 ± 1.59
			1 week	7C1 (111 mummies)	94.59 ± 2.26
		Constant
			2 weeks	7C2 (114 mummies)	93.86 ± 2.40
	7°C
			1 week	7F1 (108 mummies)	97.22 ± 1.64
		Fluctuant
			2 weeks	7F2 (107 mummies)	96.26 ± 1.90
			1 week	4C1 (112 mummies)	91.96 ± 2.72
		Constant
			2 weeks	4C2 (124 mummies)	88.71 ± 3.16
	4°C
			1 week	4F1 (101 mummies)	97.03 ± 1.70
		Fluctuant
			2 weeks	4F2 (110 mummies)	95.46 ± 2.08
			1 week	0C1 (126 mummies)	95.24 ± 2.13
		Constant
			2 weeks	0C2 (166 mummies)	80.12 ± 3.99
	0°C
			1 week	0F1 (101 mummies)	95.05 ± 2.17
		Fluctuant
			2 weeks	0F2 (120 mummies)	94.17 ± 2.34

Table 2 . The cumulative fecundity with (K) indicating the maximum of offspring after one generation and the log(3)/a indicating the inflection point, and progeny sex-ratio progeny expressed as the proportion of females for G1. Data are presented as mean ± SE (SE = standard deviation/√n) . The number between the brackets is the number of repetitions. Different letters indicate the significant differences among the treatments (p = 0.004).

 2

	Treatment	The cumulative fecundity (K value)	The inflection point (log(3)/a)	Progeny sex-ratio
	20°C (15)	52.88 ± 0.33 ab	2.72 ± 0.01 bc	0.57 ± 0.01 a
	7C1 (13)	35.64 ± 0.33 e	2.22 ± 0.04 de	0.47 ± 0.01 cde
	7C2 (13)	32.50 ± 0.31 ef	2.10 ± 0.02 ef	0.42 ± 0.01 de
	7F1 (15)	47.15 ± 0.32 c	2.05 ± 0.01 ef	0.55 ± 0.01 ab
	7F2 (13)	36.61 ± 0.20 de	2.40 ± 0.02 d	0.51 ± 0.02 abcd
	4C1 (13)	28.74 ± 0.18 f	2.18 ± 0.02 e	0.40 ± 0.01 e
	4C2 (13)	37.10 ± 0.45 de	1.82 ± 0.03 g	0.45 ± 0.02 cde
	4F1 (13)	48.24 ± 0.48 bc	2.85 ± 0.05 b	0.51 ± 0.02 abc
	4F2 (13)	41.98 ± 0.40 d	2.30 ± 0.03 de	0.47 ± 0.01 bcd
	0C1 (6)	54.66 ± 0.81 a	2.50 ± 0.03 cd	0.57 ± 0.01 ab
	0C2 (7)	37.55 ± 0.76 de	2.69 ± 0.08 bc	0.37 ± 0.04 de
	0F1 (6)	36.89 ± 0.81 de	1.86 ± 0.05 fg	0.48 ± 0.03 abcd
	0F2 (6)	38.16 ± 0.89 de	3.41 ± 0.17 a	0.48 ± 0.02 abcd

Table 3 . Demographic growth parameters in adults emerged after mummy storage, according to the storage temperature, duration and thermal regime. Data are presented as mean ± SE, obtained by the Jackknife method. Tc: development time (storage period was not taken into account), R 0 : the net reproductive rate and r m : the intrinsic rate of increase. The number between the brackets is the number of repetitions. Different letters indicate the significant differences among the treatments (p = 0.004).

 3

		Demographic parameters
	Treatment
		Tc	R 0	r m
	20°C (15)	17.44 ± 0.01 ahi	51.94 ± 0.57 a	0.232 ± 0.010 a
	7C1 (13)	15.99 ± 0.04 cdhi	35.25 ± 0.60 d	0.230 ± 0.019 a
	7C2 (13)	14.76 ± 0.02 fhi	31.49 ± 0.53 f	0.240 ± 0.016 a
	7F1 (15)	15.89 ± 0.02 dehi	47.47 ± 0.28 b	0.249 ± 0.008 a
	7F2 (13)	14.14 ± 0.02 ghi	36.62 ± 0.32 d	0.262 ± 0.009 a
	4C1 (13)	16.80 ± 0.02 bhi	27.86 ± 0.33 g	0.201 ± 0.009 a
	4C2 (13)	14.56 ± 0.05 adfhi	36.73 ± 0.84 d	0.239 ± 0.014 a
	4F1 (13)	16.04 ± 0.03 chi	38.01 ± 0.55 cd	0.242 ± 0.009 a
	4F2 (13)	14.28 ± 0.03 ehi	41.33 ± 0.73 c	0.254 ± 0.016 a
	0C1 (6)	17.32 ± 0.04 h	54.92 ± 1.81 a	0.236 ± 0.009 a
	0C2 (7)	17.52 ± 0.06 h	38.07 ± 1.75 cd	0.224 ± 0.011 a
	0F1 (6)	16.28 ± 0.09 i	38.58 ± 2.10 cd	0.242 ± 0.021 a
	0F2 (6)	16.04 ± 0.11 i	37.42 ± 2.36 cd	0.235 ± 0.018 a


Marion Varet

Françoise Burel

Julien Pétillon
email: 50.26.julien.petillon@univ-rennes1.fr

Can urban consolidation limit local biodiversity erosion? Responses from carabid beetle and spider assemblages in Western France

Keywords: City compaction, Araneae, Carabidae, housing density, arthropods

During the last decades, urban consolidation has been developed to minimize spatial expansion of cities, yet very few studies investigated whether it would actually reduce some negative effects of urbanization on biodiversity. In this study, we compared the invertebrate assemblages associated with two distinct urban forms (compact vs. conventional), focusing on two arthropod taxa often used as bioindicators, and dominant in urban habitats: spiders and carabid beetles. The following parameters were estimated: assemblage composition, species richness, activity-density total, per species (excluding seldom-recorded species) and per size class. The field collection was performed in 2009 using pitfall traps randomly set in hedgerows within 6 sites (representing 251 traps). A total of 4413 spiders belonging to 117 species and 2077 adult carabid beetles belonging to 39 species were collected. We found few significant differences in carabid beetle and spider assemblages between the two urban forms. The species richness of both groups was independent from the neighborhood design. Only four species of carabid beetles and ten of spiders significantly reacted to the neighborhood design, and no difference was found among the two designs for all other species. Large carabid beetles were more abundant and small spiders less abundant in the new neighborhood design compared to the conventional one. For both carabid beetles and spiders, no difference in assemblage composition was found between neighborhood designs. We therefore conclude that urban consolidation, by permitting a higher human density with similar arthropod assemblages, could contribute to reduce biodiversity loss in cities.

Introduction

The world's urban population has increased considerably in the recent decades, reaching around 50% of the global population at present (United Nations Population Division 2012). This growth is accompanied by an increase in the urbanization of land (Weber 2003;[START_REF] Grimm | Global change and the ecology of cities[END_REF], and frequently, negative effects on biodiversity [START_REF] Mckinney | Urbanization, biodiversity, and conservation[END_REF]. For plants, a lower α-diversity is usually found in urban habitats compared to that in rural environments (e.g. [START_REF] Mckinney | Urbanization, biodiversity, and conservation[END_REF].

Arthropod species richness is also reported to decrease along rural to urban gradients (carabid beetles: Niemelä andKotze 2009, Magura et al. 2010;carabid beetles and spiders: Varet el al. 2011; arthropods in general: [START_REF] Gibb | Habitat fragmentation in an urban environment: large and small fragments support different arthropod assemblages[END_REF]Hochuli 2002, Kotze et al. 2011), with possible risks of extinction predicted for several insect taxa [START_REF] Fattorini | Insect extinction by urbanization: A long term study in Rome[END_REF]) and related changes in trophic structure [START_REF] Chapuis | Urbanization affects the trophic structure of arboreal arthropod communities[END_REF].

Given the spread of urban areas, it is thus important to understand the functioning of urban ecosystems to plan the future development of cities and to minimize their negative environmental impacts [START_REF] Magura | Changes in carabid beetle assemblages along an urbanisation gradient in the city of Debrecen, Hungary[END_REF]). Cities exhibit a specific environment in which the conditions differ from those in natural habitats [START_REF] Semenova | Ecology of ground beetles in an industrial city[END_REF], notably by the extent of impervious surfaces (Weller and Ganzhorn 2004). However, the conservation of nature in the city is increasingly important [START_REF] Reduron | The role of biodiversity in urban areas and the role of cities in biodiversity conservation[END_REF][START_REF] Miller | Conservation where people live and work[END_REF][START_REF] Jim | Pattern and divergence of tree communities in Taipei's main urban green spaces[END_REF].

Currently, the desire and demand for nature in the city by urban residents and society in general are clearly growing [START_REF] Clergeau | Une écologie du paysage urbain[END_REF]. Thus, to meet these demands, new ways of thinking about the city and new urban forms are developed, mostly to minimize their spatial expansion [START_REF] Jenks | The compact city. A sustainable urban form? SPON[END_REF]Williams et al. 2000;Jenks and Dempsey 2005).

Urban consolidation, which aims at reducing the number of individual houses with gardens [START_REF] Grose | Changing relationships in public open space and private open space in suburbans in south-western Australia[END_REF]) in favor of grouped (semi-detached) or collective housing [START_REF] Tratalos | Urban form, biodiversity potential and ecosystem services[END_REF], is developing fast [START_REF] Searle | Urban consolidation and the inadequacy of local open space provision in Sydney[END_REF] due to several proved or supposed advantages like limited urban sprawl, a more efficient use of land, a more efficient use of services, some shorter travel distances, or a lower carbon footprint [START_REF] Dodson | In the wrong place at the wrong time? Assessing some planning, transport and housing market limits to urban consolidation policies[END_REF]). Yet some disadvantages may occur (longer travel distances to nature, less green space within the city, stormwater/air quality issues, health issues, crowding), and among them, possible negative consequences on biodiversity [START_REF] Gray | Urban consolidation, household greenhouse emissions and the role of planning[END_REF]. Very few studies have investigated the consequences of urban consolidation on biodiversity, despite obvious potential impacts [START_REF] Tratalos | Urban form, biodiversity potential and ecosystem services[END_REF]. Green spaces, developed in order to promote outdoor recreational activities, social interactions [START_REF] Grose | Changing relationships in public open space and private open space in suburbans in south-western Australia[END_REF][START_REF] Rogers | Neighbourhood design and sense of community: comparing suburban neighbourhoods in Houston Texas[END_REF] and environmental quality are used more and more by the public. Urban green spaces can potentially contribute to enhancing biodiversity in the city [START_REF] Kühn | The flora of German cities is naturally species rich[END_REF][START_REF] Jim | Pattern and divergence of tree communities in Taipei's main urban green spaces[END_REF] including through the creation of microhabitat [START_REF] Jim | Pattern and divergence of tree communities in Taipei's main urban green spaces[END_REF]. In addition, the continuity of all the green areas is taken into account with the growing concept of green urban corridors that are known to limit habitat fragmentation and to favor biodiversity conservation (e.g. Vergnes et al. 2012). As a consequence, new neighborhood designs should have higher housing density with a better continuity of public green space, thus promoting increased connectivity for biodiversity. Conversely, conventional neighborhood designs are likely characterized by a lower housing density, but with a strong fragmentation of public green space.

The aim of the present study is to investigate whether and how the type of urban form will affect two groups of arthropods (as a key component of biodiversity) in a single habitat type (hedgerows, as an important habitat for urban biodiversity: [START_REF] Lövei | The influence of matrix and edges on species richness patterns of ground beetles (Coleoptera, Carabidae) in habitat islands[END_REF]) at a given time.

Spiders and carabid beetles were selected as model groups because they are known to react strongly to changes in microhabitat conditions and therefore are often used as bioindicators [START_REF] Marc | Spiders (Araneae) useful for pest limitation and bioindication[END_REF][START_REF] Bell | The implications of grassland and heathland management for the conservation of spider communities: a review[END_REF][START_REF] Luff | Classification and prediction of grassland habitats using ground beetles (Coleoptera, Carabidae)[END_REF][START_REF] Rainio | Ground beetles (Coleoptera: Carabidae) as bioindicators[END_REF][START_REF] Pearce | The use of ground beetles (Coleoptera: Carabidae) and spiders (Araneae) as bioindicators of sustainable forest management: A review[END_REF]. They are also among the most diversified groups of ground-dwelling arthropods in urban habitats (e.g. [START_REF] Dias | Species richness and seasonality of spiders (Arachnida, Araneae) in an urban Atlantic forest fragment in Northeastern Brazil[END_REF][START_REF] Sattler | Urban arthropod communities: added value or just a blend of surrounding biodiversity?[END_REF]Vergnes et al. 2012). In this research we tested the following hypotheses more specifically. Hypothesis 1: The new neighborhood designs with more public green spaces and hedgerows should accommodate more species and individuals (total and by species). Hypothesis 2: The conventional neighborhood designs with less dense and more fragmented public green spaces and hedgerows should accommodate more species with high dispersal ability (the mean size of species was used here as a broad, negative proxy of longdistance dispersal abilities: Southwood 1962; [START_REF] Magura | Body size inequality of carabids along an urbanisation gradient[END_REF][START_REF] Desender | Een nieuwe verspreidingsatlas van de loopkevers en zandloopkevers (Carabidae) in België[END_REF]; yet large species tend to cover longer distances when they actively disperse: [START_REF] Jeannel | Faune de France 39 Coléoptères carabiques[END_REF]). The assumed differences in landscape parameters between the two designs were also tested for our six study sites.

Materials and methods

Study sites and sampling design

To compare new and conventional urban designs, six neighborhoods, three of each type, were selected within the conurbation of Rennes (Fig. 1). They are located in six cities: Brécé (N 48° 23', W 0° 48', coded A), Vezin-le-Coquet (N 48° 7', W 1° 45', coded B), Pacé (N 48° 8', W 1° 46', coded C) (A to C: conventional design), Chantepie (N 48° 5', W 1°37', coded D), Saint Jacques de la Lande (N 48° 3', W 1° 43', coded E) and Le Rheu (N 48° 6', W 1° 48', coded F) (D to F: new design). All neighborhoods were built during the same period of time (between 1997 and 2000) and were adjacent to rural areas (field or meadow, so the colonization from surrounding habitats is thus not seen as limited; Varet et al. 2011). Their area varied from 10 ha to 14.5 ha. All sites were mapped using ArcView by interpretation of orthophotographs (2006), cadastral data and ground-truthing. Mean house density was two times higher in the new neighborhood design compared to that in the conventional one (31 vs. 16 houses/ha, respectively). Sample points were randomly selected (Arcview, Geo Wizards) within public hedgerows, and spaced at least by 10 meters so that the traps were considered independent [START_REF] Topping | Limitations in the use of pitfall traps in ecological studies exemplified by a study of spiders in a field of winter wheat[END_REF]. Hedgerows were planted and designed at the creation of the neighborhood.

Each sample point consisted of one pitfall trap (diameter at the surface: 85mm) covered with a plastic roof. The pitfall traps were filled with a preservation solution composed of 50% monopropylene glycol and 50% aqueous salt solution of 100g/l (best fluid for collecting grounddwelling spiders; [START_REF] Schmidt | Capture efficiency and preservation attributes of different fluids in pitfall traps[END_REF]. At each site, between 40 and 44 traps were set up and collected (some traps were stolen or damaged during the sampling period, which was taken into account by dividing the total catches of each trap by the effective collection, see below). The pitfall traps were emptied every two weeks for eight weeks between mid-April 2009 and mid-June 2009. The temporal sampling effort was consequently limited to favor a larger spatial extent (e.g. [START_REF] Rudulier | Can carabidologists spot a pitfall? The non-equivalence of two components of sampling effort in pitfall-trapped ground beetles (Carabidae)?[END_REF]; other studies in the same area also showed that most carabid beetle and spider species were collected during the spring compared to an annual sampling (sampling in one site over 3 years and use of rarefaction methods in three sites; Varet 2011).

Each site was characterized by the following landscape variables: length, number and mean length of public hedgerows, proportion of public green space, number and mean size of public green patches, shortest distance between two patches and index of contagion. One meter around each pitfall trap, the following parameters were measured: litter depth (from 1=thin to 3=thick), presence of grass, shrub and tree strata, origin of plant species (local and/or exotic).

Species identification and classification

Carabid beetles and spiders were preserved in 70% ethanol and stored in the University collection (Rennes, France). Adult carabid beetles were identified using [START_REF] Jeannel | Faune de France 39 Coléoptères carabiques[END_REF][START_REF] Jeannel | Faune de France 39 Coléoptères carabiques[END_REF] and [START_REF] Trautner | Tiger beetles, ground beetles: illustrated key to the Cicindelidae and Carabidae of Europe[END_REF], whereas adult spiders were identified using [START_REF] Roberts | The spiders of Great Britain and Ireland, Volumes 1 and 2[END_REF][START_REF] Roberts | The spiders of Great Britain and Ireland, Volumes 1 and 2[END_REF] and [START_REF] Heimer | How landscape structure, land-use intensity and habitat diversity affect components of total arthropod diversity in agricultural landscapes[END_REF]. Catches in pitfall traps were related to trapping duration and pitfall perimeter in order to calculate an 'activity trappability density' (number of individuals per day and per meter; [START_REF] Sunderland | Density estimation for invertebrate predators in agroecosystems[END_REF], further abbreviated as 'activitydensity'. Carabid beetles and spiders were classified into size classes (using mainly [START_REF] Roberts | The spiders of Great Britain and Ireland, Volumes 1 and 2[END_REF] for spiders and Bouget 2004 for carabid beetles). The size classes (in mm, respectively size1, size2, size3) were 0-3, 3-5, ≥5 for adult spiders and 0-5, 5-10, ≥10 for carabid beetles.

Statistical analysis

We performed multivariate analyses of activity-density of all species using the software

Results

Description of the neighborhood designs

The analysis of the landscape structure of the 6 neighborhoods from the 2 designs revealed that the number of green patches and the length of public hedges were higher in the new neighborhood design and that the index of contagion was almost significantly higher in the new neighborhood design while the other parameters were not significantly different between the two urban designs (Table 1). All sites were characterized by hedgerows with a medium-depth litter, low percentages of herbaceous and tree strata, dense shrubs, and a dominance of local plant species compared to exotic species (Table 1).

Description of the fauna

In total, 2077 carabid specimens belonging to 39 species were collected. Individuals of Nebria brevicollis accounted for more than 50% of the total catch. The number of species varied

Species assemblages vs. urban forms

Axis 1 of the CA on carabid beetle assemblages (Fig. 2) represented 10.3% of inertia and Axis 2, 8% of inertia. Axis 1 of the CA on spider assemblages (Fig. 3) represented 5.7% of inertia and Axis 2, 5% of inertia. The neighborhood design variable on axis 1 and 2 of CAs was very close to the origin for both groups, and neighborhood designs cannot be segregated by the global composition of assemblages, (Figs. 2 and3).

Species activity-density and richness vs. urban forms

The total activity-density of carabid beetles was significantly higher in the new neighborhood design while the total activity-density of spiders and the species richness of both groups were independent from the neighborhood design. Several species were significantly associated with the neighborhood design. The carabid beetles Harpalus rufipes and N. brevicollis and the spider D. erythrina were significantly more abundant in the new neighborhood design, while the carabid beetles Asaphidion stierlini and Pterostichus melanarius and the spiders Agoeca inopina, Alopecosa pulverulenta, Hahnia nava, Pachygnatha degeeri, Pardosa amentata, Pardosa saltans, Phrurolithus festivus, T. ruricola and Z. italicum were significantly more abundant in the conventional neighborhood design. Large carabid beetles (size class 3: Table 2) were more abundant and small spiders (size class 1: Table 3) less abundant in the new neighborhood design compared to the conventional one.

Discussion

From a strictly urbanistic point of view, the two urban forms are obviously distinct (type and density of housing, coverage ratio, floor area ratio; [START_REF] Chapuis | Urbanization affects the trophic structure of arboreal arthropod communities[END_REF]), but from a landscape perspective, the distinction was less obvious in this study. In terms of composition, urban forms could be distinguished according to two parameters. The higher density and length of hedgerows and the higher number of public green space patches in the new urban design are in accordance with the goals aimed at the conception of these neighborhoods, and supported our hypotheses.

Regarding landscape connectivity, both urban forms were not really different. Indeed, whatever the urban form, the neighborhood was split by dense public roads. This analysis at a landscape scale of the two urban forms was yet based on six sites only, and nevertheless there was a trend for the new, compact, urban form to offer a better connectivity between green habitats. The goals set by new urban form designers are thus not all reached here. Several, although not numerous, species had some population activity-densities dependent on urban form. Most of these species were more abundant in neighborhoods of conventional design.

This can be explained by the fact that most of these species are generalist or open field species, like the carabids Asaphidion stierlini and Pterostichus melanarius [START_REF] Luff | Provisional atlas of the ground beetles (Coleoptera, Carabidae) of Britain[END_REF][START_REF] Bouget | Chablis et diversité des coléoptères en forets feuillus de plaine: Impact à court terme de la trouée, de sa surface et de son contexte paysager[END_REF]) and the spiders Agoeca inopina, Alopecosa pulverulenta, Pachygnatha degeeri, Pardosa amentata, Phrurolithus festivus, T. ruricola and Z. italicum [START_REF] Hänggi | Habitats of central European spiders. Centre Suisse de cartographie de la faune[END_REF]Harvey et al. 2002).

Indeed, the conventional neighborhood has a lower density of public hedgerows and is consequently likely to host more species preferring open environments. Yet, two forest species, the spiders Hahnia nava and Pardosa saltans, were significantly more abundant in the conventional design than in compact neighborhoods, but they occurred at low numbers in both urban forms (although sufficient to be included in the individual species analysis). More generally, forest species were little represented in both urban forms and species richness of carabid beetles and spiders did not differ among the neighborhoods, contrary to our first hypothesis with the activity-density of forest species not higher in new urban forms. This can be partly due to the similarity of the urban forms when considering certain landscape indexes. Indeed, the diversity of assemblages is partly shaped by the landscape structure (e.g. [START_REF] Coeur | Why and how we should study field boundaries biodiversity in an agrarian landscape context[END_REF][START_REF] Schmidt | Differential effects of landscape and management on diversity and density of ground-dwelling farmland spiders[END_REF][START_REF] Schweiger | Quantifying the impact of environmental factors on arthropod communities in agricultural landscapes across organizational levels and spatial scales[END_REF][START_REF] Heimer | How landscape structure, land-use intensity and habitat diversity affect components of total arthropod diversity in agricultural landscapes[END_REF]. But habitat quality (including frequency and intensity of disturbances) also determines the local presence of specialist or generalist species. The lack of an effect of urban forms on species richness, as well as the low occurrence of forest species, can then be also attributed to the similarity in quality and management of the hedgerows between the two urban forms. It should be emphasized that hedgerows in both new and conventional urban forms are managed by the same people, who apply their skills independently from the urban form itself (in the conurbation of Rennes; Le [START_REF] Rudulier | Can carabidologists spot a pitfall? The non-equivalence of two components of sampling effort in pitfall-trapped ground beetles (Carabidae)?[END_REF]). Yet the management of green spaces made up of non-native species may recreate and maintain some diversified assemblages (e.g. for carabid beetles; [START_REF] Magura | Effects of nature management practice on carabid assemblages (Coleoptera: Carabidae) in a non-native plantation[END_REF], intensive management is well-known to homogenize invertebrate faunas, and maintain species of young successional stages even in older neighborhood (comparisons between 14 and 30 year-old sites in the same study area; Varet et al. in press.).

Confirming our second hypothesis, the total activity-density of large individuals (carabid beetles) was higher and small individuals (spiders) were lower in the new urban design than in the conventional urban designs with individual houses and gardens. Large individuals (carabid beetles), considered to have a lower dispersal capacity [START_REF] Den Boer | Dispersal power and survival of carabids in a cultivated countryside[END_REF][START_REF] Dajoz | Size and phenology of ballooning spiders at two locations in eastern Texas[END_REF], are more numerous in new urban designs. These designs include more hedgerows and seem to offer a better connectivity than conventional designs. New urban designs include more continuous suitable elements, favoring the dispersal of large carabid individuals [START_REF] Burel | Landscape structure effects on carabid beetles spatial patterns in western France[END_REF], as opposed to neighborhoods with more fragmented public green spaces and hedgerows due to individual houses. Small individuals (spiders), considered as having a higher dispersal capacity (size and mass limitation of long-distance dispersal in spiders; e.g. [START_REF] Coyle | Ballooning mygalomorphs: estimates of the masses of Sphodros and Ummidia ballooners (Araneae: Atypidae, Ctenizidae)[END_REF], were also more numerous in conventional neighborhoods. The lower number of hedgerows in these neighborhoods allows for a better dispersal of small spiders using ballooning as a main dispersal method [START_REF] Dajoz | Size and phenology of ballooning spiders at two locations in eastern Texas[END_REF], mostly by decreasing the number of barriers to (aerial) dispersers [START_REF] Larrivée | Diversity of canopy and understorey spiders in north-temperate hardwood forests[END_REF].

Although obvious differences in some landscape parameters were highlighted, only slight, mostly non-significant differences were found in arthropod assemblages, despite the use of complementary biological models (e.g. [START_REF] Desender | Diversity and conservation of terrestrial arthropods in tidal marshes along the River Schelde: a gradient analysis[END_REF][START_REF] Pétillon | Influence of abiotic factors on spider and ground beetles communities in different salt-marsh systems[END_REF]). This can be explained by the fact that urban environments, whatever their design, are considered highly disturbed [START_REF] Blair | Land use and avian species diversity along an urban gradient[END_REF][START_REF] Ormerod | Restoration in applied ecology: editor's introduction[END_REF] and consequently host mostly species of young successional stages. This study also underlines the need to conduct trait-based analyses on top of classical species richness approach (see also [START_REF] Magura | A species-level comparison of occurrence patterns in carabids along an urbanisation gradient[END_REF][START_REF] Tóthmérész | Responses of carabid beetles to urbanization in Transylvania (Romania)[END_REF][START_REF] Horváth | Ignoring ecological demands masks the real effect of urbanization: a case study of ground-dwelling spiders along a rural-urban gradient in a lowland forest in Hungary[END_REF]. As an applied conclusion, urban consolidation, by permitting a higher housing density with similar arthropod assemblages, is likely to reduce biodiversity loss in cities.

Table 1: Landscape indexes for each neighborhood and comparison of means between the two urban designs (significance by Mann-Whitney tests indicated with bold font). Bold font indicates significant difference among urban designs. For information, the following local parameters are also provided: mean litter depth (see the scores in Material and Methods), occurrence of grass, shrub and tree strata and local and exotic species.

  CANOCO (ter Braak and Šmilauer 2002) in order to analyze the patterns of species composition in the 6 sites. The choice between linear (Principal Component Analysis: PCA) or unimodal (Correspondence Analysis: CA) analyses depended on the length values of the first axis gradient previously realized with DCA (Detrended Correspondence Analysis). To test for differences in activity-density (total, per species represented by more than 1% of total catches and per size class) and species richness between the neighborhood designs, we used nested general linear model (GLM) with a quasi-Poisson distribution performed using data from the individual traps(Vincent and Haworth 1983;[START_REF] O'hara | Do not log-transform count data[END_REF]. City was nested within neighborhood design. The resulting data were analyzed with R software (R Development Core Team 2009) using the glmmPQL package (e.g.Venables and Ripley, 2002).

  between the 6 neighborhoods (site A: 21, B: 21, C: 27, D: 17, E: 14, F: 20), as did the number of individuals (site A: 249, B: 130, C: 423, D: 283, E: 158, F: 834). In total, 4413 spider specimens belonging to 117 species were collected. Individuals of Pardosa hortensis, Pardosa prativaga, Ozyptila praticola, Zodarion italicum, Dysdera erythrina and Trochosa ruricola accounted for more than 40% of the total catch. The number of species and individuals were similar in all neighborhoods (between 55 and 73 species; site A: 55, B: 73, C: 70, D: 71, E: 67, F: 58; and between 616 and 891 individuals; site A: 714, B: 616, C: 891, D: 767, E: 742, F: 683).

Fig. 3 .

 3 Fig. 3. Ordination diagram of the first two axes of Corresponding Analysis for 69 spider

Fig

  Fig. 2.

Table 2 .

 2 Result of the GLM analysis of the effect of neighborhood design (CD=Conventional design; ND=new design) on species richness and activity-density (total, mean per species and per size class) for the most abundant carabid beetle species (i.e. represented by at least 1% of total catches). Bold font indicates significant difference among urban designs.

		New design Site D Site E	Site F	Conventional design Site A Site B Site C	U-value	p-value
	length of public edges (m) 281.6	335.5	252.9	138	221.1	95.5	U1=0 (U2=9)	0.0495
	number of public edges	6.4	9	9.1	3.6	9.1	1.5	U1=2.5 (U2=6.5)	0.3827
	mean length of public edges (m)	44.1	37.4	27.9	38.6	21.4	66	U1=4 (U2=5)	0.8273
	the proportion of public green space	34.4	34.3	13.3	12.3	22.6	11.6	U1=1 (U2=8)	0.1266
	number of public green patches	4.3	3.9	5.1	2.4	3.6	2.7	U1=0 (U2=9)	0.0495
	mean size of public green patch (ha)	756	884	261	502	621	421	U1=3 (U2=6)	0.5127
	the shortest distance between two patches (m)	5.3	4.2	6.3	8.1	4.4	9.9	U1=2 (U2=7)	0.2752
	index of contagion	35	36	38	35	32	34	U1=0.5 (U2=8.5)	0.0765
	Mean litter depth	2.23	1.80	1.43	1.86	1.71	1.84
	Occurrence (%) of
	Herbaceous stratum	43.18	40.91	11.36	42.11	32.56	55.26
	Shrub stratum	100	100	100	100	100	100
	Tree stratum	25.00	15.90	0	0	25.58	23.68
	Native species	68.18	51.16	81.81	97.37	74.42	50.00
	Exotic species	40.91	60.47	34.09	44.74	39.53	63.16

Table 3 .

 3 Result of the GLM analysis of the effect of neighborhood design (CD=Conventional design; ND=new design) on species richness and activity-density (total, mean per species and per size class) for the most abundant spider species (i.e. represented by at least 1% of total catches). Location of the 6 neighborhoods (conurbation of Rennes, Brittany, France); sites A to C have conventional designs and sites D to F have new designs. Ordination diagram of the first two axes of Corresponding Analysis for 26 carabid beetle species and 251 samples. For projection, the species fit range is from 3% to 100%; 14 species are represented. The inverted triangle represents the new neighborhood design and the star represents the conventional neighborhood design. Species codes are given in Table2 and:Haru=Harpalus rubripes (De Geer, 1774); Lefu=Leistus fulvibarbis (Dejean, 1826); Lopi=Loricera pilicornis (Fabricius, 1775); Trec=Trechus sp.

				Effect of city	Effect of neighborhood design
	Genus species	Authority, year	code
				F-ratio	p-value	Means in ND	Means in CD	F-ratio p-value	result
	Agroeca inopina	Cambridge, 1886	Agrin	2.44	0.047	0.009 ±0.003 0.018 ±0.004 4.47	0.036	ND<CD
	Alopecosa pulverulenta	(Clerck, 1757)	Alopu 6.07	<0.001	0.017 ±0.003 0.041 ±0.013 6.98	0.009	ND<CD
	Clubiona comta	Koch, 1839	Cluco	5.34	<0.001	0.018 ±0.004 0.018 ±0.004 0.01	0.906
	Clubiona terrestris	Westring, 1851	Clute	2.22	0.07	0.016 ±0.003 0.012 ±0.003 0.72	0.397
	Diplostyla concolor	(Wider, 1834)	Dipco	0.89	0.47	0.009 ±0.002 0.014 ±0.003 2.25	0.14
	Drassodes lapidosus	(Walckenaer, 1802)	Drala	7.96	<0.001	0.015 ±0.003 0.013 ±0.004 0.35	0.555
	Dysdera erythrina	(Walckenaer, 1802)	Dyser	3.10	0.016	0.046 ±0.008 0.026 ±0.005 4.87	0.028	ND>CD
	Enoplognatha thoracica	(Hahn, 1833)	Enoth	5.03	<0.001	0.012 ±0.003 0.022 ±0.007 2.98	0.085
	Erigone dentipalpis	(Wider, 1834)	Eride	1.88	0.120	0.017 ±0.005 0.011 ±0.005 0.1.00	0.319
	Hahnia nava	(Blackwall, 1841)	Hahna 1.71	0.148	0.008 ±0.002 0.027 ±0.006 10.37	0.001	ND<CD
	Microneta viaria	(Blackwall, 1841)	Micvi	4.07	0.003	0.028 ±0.004 0.022 ±0.005 1.27	0.261
	Neriene clathrata	(Sundevall, 1830)	Nercl	1.83	0.124	0.020 ±0.004 0.017 ±0.004 0.36	0.549
	Ozyptila praticola	(Koch, 1837)	Ozypr	3.82	0.005	0.079 ±0.010 0.068 ±0.009 0.69	0.406
	Pachygnatha degeeri	Sundevall, 1829	Pacde	6.62	<0.001	0.009 ±0.003 0.023 ±0.008 5.42	0.021	ND<CD
	Pardosa amentata	(Clerck, 1757)	Param 4.93	<0.001	0.002 ±0.002 0.027 ±0.015 12.76	<0.001	ND<CD

Acknowledgements

We would like to thank Anne Treguier and Béatrice Sauzeau, Alain Canard, Robert Bosmans and Christophe Hervé for their help in identifying carabid beetles and problematic spiders, respectively. Sandrine Baudry, Aldyth Nys, two anonymous referees and the associated editor are acknowledged for their comments on earlier drafts. This study was funded by Rennes Métropole and the 'Ministère de l'Enseignement supérieur et de la Recherche' (grant 'CIFRE' to M.V.).