Bertrand Kokolo
email: bertrandkokolo@yahoo.fr

Christiane Attéké

Boris Achille

Eyi Mintsa

Brama Ibrahim

Doyle Mckey

Rumsais Blatrix

Christiane Atteke

Ibrahim Brama

Keywords: ant-plant symbiosis, chemical mediation, defence, protection mutualism, specificity

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Introduction

Ant-plant interactions, particularly protection mutualisms [START_REF] Heil | Protective ant-plant interactions as model systems in ecological and evolutionary research[END_REF], are widespread in tropical rain forests. In addition to numerous non-symbiotic interactions mediated by plant-provided food sources such as extrafloral nectar [START_REF] Heil | Extrafloral nectar at the plant-insect interface: a spotlight on chemical ecology, phenotypic plasticity, and food webs[END_REF], symbiotic mutualisms also occur. In these, myrmecophytic plants provide nesting space in the form of hollow twigs, petioles, stipules, leaf pouches, etc.-more or less specialized structures termed domatia-and food in the form of extrafloral nectar, food bodies, secretions of plant-nourished hemipteran trophobionts, or combinations of these, to their host ants (Davidson & McKey 1993[START_REF] Mckey | The trophic structure of tropical ant-plant-herbivore interactions: community consequences and coevolutionary dynamics[END_REF]. In return, ants defend their host plant against herbivores and pathogens ( [START_REF] Letourneau | Ants, stem-borers, and fungal pathogens: experimental tests of a fitness advantage in Piper ant-plants[END_REF][START_REF] Rosumek | Ants on plants: a meta-analysis of the role of ants as plant biotic defenses[END_REF]. About 700 plant and 110 ant species are involved in this type of symbiosis (Chomicki & Renner 2015, Davidson & McKey 1993). In some cases, the interaction is obligatory for one or even both partners [START_REF] Gaume | An ant-plant mutualism and its host-specific parasite: activity rhythms, young leaf patrolling, and effects on herbivores of two specialist plant-ants inhabiting the same myrmecophyte[END_REF][START_REF] Moog | The association of the plant-ant Cladomyrma with plants in southeast Asia[END_REF][START_REF] Yu | Experimental studies of species-specificity in Cecropia-ant relationships[END_REF].

Protection of myrmecophytic plants by ants has been thoroughly studied [START_REF] Janzen | Coevolution of mutualism between ants and acacias in Central America[END_REF][START_REF] Rosumek | Ants on plants: a meta-analysis of the role of ants as plant biotic defenses[END_REF]. Like many other plants, myrmecophytic plants release volatile compounds, to which their resident ants are attracted (reviewed in Blatrix & Mayer 2010). Whereas the role of chemical signalling in ant-plant symbioses has been demonstrated by several studies, a smaller number of studies show that vibrations produced by herbivore movement also induce ant patrolling (Dejean et al. 2008[START_REF] Moog | The association of the plant-ant Cladomyrma with plants in southeast Asia[END_REF][START_REF] Federle | The two-partner ant-plant system of Camponotus (Colobopsis) sp. 1 and Macaranga puncticulata (Euphorbiaceae): natural history of the exceptional ant partner[END_REF][START_REF] Lapola | Contrasting responses to induction cues by ants inhabiting Maieta guianensis (Melastomataceae)[END_REF][START_REF] Madden | Symbiotic ants as an alternative defense against giraffe herbivory in spinescent Acacia drepanolobium[END_REF].

Protection level often differs among systems depending on the capacity of the ants to counter plant enemies (Bruna et al. 2004[START_REF] Lapola | Contrasting responses to induction cues by ants inhabiting Maieta guianensis (Melastomataceae)[END_REF]. This capacity may partly depend on colony size (Duarte [START_REF] Rocha | Bigger ant colonies reduce herbivory and herbivore residence time on leaves of an ant-plant: Azteca muelleri vs. Coelomera ruficornis on Cecropia pachystachya[END_REF], which in turn depends strongly on plant investment in the resident ant colony. Both protective behaviour and the level of plant investment in ants are driven by coevolution. However, studies comparing the efficiency with which different ants protect the same plant species have so far compared ants belonging to different genera that have independently evolved associations with the same host plant (Bruna et al. 2004[START_REF] Lapola | Contrasting responses to induction cues by ants inhabiting Maieta guianensis (Melastomataceae)[END_REF]. These studies thus cannot distinguish differences that may have resulted from coevolutionary interactions with the host plant from those that already existed prior to their host associations.

In this study we compare the level of protection conferred on host plants by two closely related species of Tetraponera (Pseudomyrmecinae), T. aethiops Smith, 1877 and T. latifrons (Emery, 1912), that both live in symbiotic associations with myrmecophytes of the genus Barteria (Passifloraceae), suggesting that their common ancestor was also a symbiont of the plants' common ancestor. Differences in their protective behaviour thus evolved in the context of this symbiosis. Comparison of their protective behaviour can thus shed light on differences driven by coevolutionary interactions. As association specificity seems weaker for B. dewevrei than for B. fistulosa, coevolution between B. fistulosa and T. aethiops might be more intensive than between B. dewevrei and T. latifrons. We postulated that more intensive coevolution of ant and plant may have resulted in better protection of B. fistulosa by its ant associate T. aethiops.

We tested the following hypotheses: (1) protective behaviour is elicited by vibration and/ or chemical signals, (2) protective behaviour of each ant species is more pronounced toward its main host plant than toward the other Barteria species, (3) T. aethiops shows a more pronounced protective behaviour than T. latifrons.

Methods

Study species and study sites

The genus Barteria (Passifloraceae) comprises four tree species (Breteler 1999) endemic to central Africa. Barteria solida Breteler does not host ants. Barteria fistulosa Mast., B. dewevrei De Wild. & T. Durand and B. nigritana Hook. f. are myrmecophytes with hollow lateral branches. Barteria nigritana hosts various opportunistic species of ants, some of which provide some protection to their host [START_REF] Djiéto-Lordon | Symbiotic mutualism with a community of opportunistic ants: protection, competition, and ant occupancy of the myrmecophyte Barteria nigritana (Passifloraceae)[END_REF].

Barteria dewevrei and B. fistulosa have three potential ant symbionts: Tetraponera aethiops, T. latifrons and Crematogaster sp. However, B. dewevrei preferentially hosts T. latifrons or Crematogaster sp., whereas B. fistulosa hosts T. aethiops preferentially, even when both Barteria and both Tetraponera species occur in syntopy [START_REF] Kokolo | Pattern of specificity in the tripartite symbiosis between Barteria plants, ants and Chaetothyriales fungi[END_REF].

Barteria fistulosa is restricted to the tropical rain-forest environment, whereas B. dewevrei occurs in a wider range of habitats: rain forest, forest gallery and the forest/savanna ecotone. Protection of B. dewevrei by its ants has never been studied. The vigorous protection of B. fistulosa by T. aethiops is well-known by local people and has been the subject of several studies (Dejean et al. 2008[START_REF] Janzen | Protection of Barteria (Passifloraceae) by Pachysima ants (Pseudomyrmecinae) in a Nigerian rainforest[END_REF][START_REF] Mckey | Ant-plants: selective eating of an unoccupied Barteria by a Colobus monkey[END_REF]. The association between the two Barteria and their two Tetraponera ants shows a high degree of specificity: Tetraponera aethiops and T. latifrons have never been found nesting outside either B. fistulosa or B. dewevrei. Moreover, B. fistulosa does not grow well if not occupied by one or the other of these two Tetraponera species. Barteria dewevrei seems to be less dependent upon Tetraponera ants, at least in some habitats, as many individual trees in some savanna sites are occupied by Crematogaster.

The experiments were conducted on 20 individuals of B. dewevrei occupied by T. latifrons in Souba (01°36'S, 14°03'E) and 20 individuals of B. fistulosa occupied by T. aethiops in Bongoville (1°37'S; 13°54'E). Souba is located at ~550 m asl on the Batéké Plateau, a highland covered by grassland and wooded savanna, criss-crossed by gallery forest. Bongoville is located at the foot of the Batéké Plateau, at ~400 m asl, along a stream in a tropical rain-forest environment.

Behavioural response of the ants to host plant disturbance

Behavioural tests were conducted in three steps. The first step aimed at measuring the spontaneous level of ant patrolling activity on leaves, i.e. without any disturbance of the tree, as a control. Two leaves were randomly selected among the young leaves of two upper branches on each Barteria individual (one leaf per branch). Starting at an arbitrary time, we recorded the time lapse before each leaf was reached by a resident ant, once per leaf. We averaged the time lapse over the two leaves for each tree. This average was meant to temper the effect of heterogeneity expected with low levels of patrolling, and was used as a single value for each tree (undisturbed leaf = control leaf).

The second step aimed at testing the effect on ant reaction of physical damage to a leaf (simulating an attack by a small herbivore, such as a phytophagous insect) and of slight vibration, which inevitably accompanies such experimental infliction of damage. Two leaves were randomly selected among the young leaves of two upper branches on each Barteria individual (one leaf per branch). The apex of one of the two leaves was cut with scissors (damaged leaf), and the other leaf was simply gently scraped superficially with the tip of scissors without inflicting damage ('scraped leaf'). For each of the two leaves simultaneously we recorded the time lapse before it was reached by a resident ant, and the number of ants that touched the site of damage (damaged leaf only) over 30 min. The two focal ant species, T. latifrons and T. aethiops, are very sensitive to physical disturbance of their host tree by an experimenter. They literally pour out of the hollow branches as soon as an experimenter manipulates, or even touches, the leaves.

Any vibration, even weak, such as cutting a leaf with scissors, may thus induce such a reaction. Damaging the leaf necessarily implies also provoking vibrations. The level of vibration we applied to the leaf by scraping it with the tip of the scissors was meant to mimic that experienced by the leaf damaged with scissors. We recognize that scraping a leaf does not exactly reproduce the same physical disturbance caused by cutting the leaf blade with scissors. However, slightly scraping the leaf was the best proxy we could use to control for a possible effect of the physical disturbance of cutting with scissors to test for the effect of emission of volatile compounds after such damage. Thus, the effect of damaging the leaf was tested by comparing the scraped and the damaged leaves (because the damage treatment corresponds to vibration + physical damage). The effect of scraping the leaf was tested by comparing the undisturbed and the scraped leaves.

The third step aimed at testing specificity of the behavioural response of the ant species to physical damage of the two plant species. On a leaf of each Barteria individual we placed a damaged leaf (apex cut with scissors) of the other Barteria species and recorded the time lapse before it was contacted by a resident ant. The host leaf upon which the damaged non-host leaf was placed was gently scraped to mimic the level of vibration of a leaf damaged with scissors, so we could compare time lapse of response to the damaged host leaf and to the damaged non-host leaf. We also compared responses of the two ant species to each treatment.

Statistical tests were performed with R 3.1.0. P-values were adjusted using Holm's method in the case of multiple comparisons.

Results

The time lapse before the ants reached the focal leaves varied significantly across treatments (host leaf undisturbed, host leaf scraped, host leaf damaged, non-host leaf damaged) for T. aethiops (Friedman test, statistic = 38, P = 0.000000036) and for T. latifrons (Friedman test, statistic = 36, P = 0.000000050).

Tetraponera latifrons ants reached the scraped host leaf significantly more quickly than the undisturbed leaf (mean ± SD, scraped: 9.5 ± 1.9 min, undisturbed: 16.3 ± 5.7 min; Wilcoxon signed-rank test, V = 8, P adj = 0.0025, Figure 1), the damaged host leaf significantly more quickly than the scraped host leaf (damaged: 7.8 ± 1.9 min, scraped: 9.5 ± 1.9 min; V = 96, P adj = 0.020, Figure 1), and the damaged host leaf (B. dewevrei) significantly more quickly than the damaged non-host leaf (B. fistulosa) (damaged host: 7.8 ± 1.9 min, damaged non-host: 10.8 ± 2.1 min; V = 171, P adj = 0.0014, Figure 1). Moreover, the number of ants of this species that touched the damaged site was significantly greater for the host leaf (B. dewevrei) than for the nonhost leaf (B. fistulosa) (damaged host: 9.1 ± 3.5 ants, damaged non-host: 6.6 ± 2.1 ants; V = 152, P adj = 0.045, Figure 1).

Tetraponera aethiops ants reached the scraped host leaf significantly more quickly than the undisturbed leaf (mean ± SD, scraped: 5.2 ± 3.0 min, undisturbed: 16.6 ± 5.3 min; Wilcoxon signed-rank test, V = 1, P adj = 0.00087, Figure 1). The time lapse before T. aethiops ants reached the host leaf did not differ significantly between scraped and damaged leaves (scraped: 5.2 ± 3.0 min, damaged: 4.5 ± 2.6 min; V = 114; P adj = 0.46, Figure 1). Tetraponera aethiops ants reached the damaged host leaf (B. fistulosa) significantly more quickly than the damaged non-host leaf (B. dewevrei) (damaged host: 4.5 ± 2.6 min, damaged non-host: 7.15 ± 2.5 min; V = 178, P adj = 0.0036, Figure 1). Moreover, the number of ants of this species that touched the damaged site was significantly greater for the host leaf (B. fistulosa) than the non-host leaf (B. dewevrei) (damaged host: 15.2 ± 4.0 ants, damaged non-host: 13.3 ± 3.3 ants; V = 162, P adj = 0.045, Figure 1).

The time lapse before the ants reached the undisturbed leaf did not differ significantly between the two ant species (mean ± SD, T. latifrons: 16.3 ± 5.7 min, T. aethiops: 16.6 ± 5.3 min; Mann-Whitney U-test, W = 191, P adj = 0.81), indicating no significant difference in the spontaneous level of patrolling activity. Tetraponera aethiops ants reached their host leaf (B. fistulosa) significantly more rapidly than T. latifrons reached theirs (B. dewevrei), whether leaves were simply scraped (T. aethiops: 5.2 ± 3.0 min, T. latifrons: 9.5 ± 1.9 min; W = 344, P adj = 0.00084) or damaged (T. aethiops: 4.5 ± 2.6 min, T. latifrons: 7.8 ± 1.9 min; W = 336, P adj = 0.0014). Moreover, the number of T. aethiops ants that contacted the damaged host leaf during 30 min was significantly larger than for T. latifrons (T. aethiops: 15.2 ± 4.0 ants, T. latifrons: 9.1 ± 3.5 ants; W = 345, P adj = 0.0000029). Tetraponera aethiops ants were significantly faster and more numerous than T. latifrons in contacting the damaged non-host leaf (T. aethiops on B. dewevrei: 7.15 ± 2.5 min, 13.3 ± 3.3 ants; T. latifrons on B. fistulosa: 10.8 ± 2.1 min, 6.6 ± 2.1 ants; time lapse: W = 55, P adj = 0.00078; number of ants: W = 383, P adj = 0.0000029).

Discussion

Behavioural response of Tetraponera ants to disturbance of their Barteria host plants

Most ants associated with myrmecophytes respond to leaf damage in less than five minutes (reviewed in Blatrix & Mayer 2010). The time lapse before T. aethiops and T. latifrons reached a damaged leaf appeared comparatively long (4.5 ± 2.6 and 7.8 ± 1.9 min, respectively), when we consider that the Tetraponera ants associated with Barteria are well known for their particularly prompt aggressive reaction to human intruders [START_REF] Janzen | Protection of Barteria (Passifloraceae) by Pachysima ants (Pseudomyrmecinae) in a Nigerian rainforest[END_REF]). As we were aware of this particularity, we took special care to limit physical disturbance as much as possible when manipulating experimental leaves ("scraped" and "damaged" treatments). The treatments we applied were probably more representative of the disturbance induced by small insects than that induced by mammals. Comparing the African Barteria/Tetraponera symbiosis with the American Acacia/Pseudomyrmex symbiosis, [START_REF] Janzen | Protection of Barteria (Passifloraceae) by Pachysima ants (Pseudomyrmecinae) in a Nigerian rainforest[END_REF] noted that the protection behaviour displayed by Tetraponera aethiops is particularly adapted to protect its host plant against large herbivores such as mammals. For instance, the number of workers of Tetraponera aethiops patrolling Barteria fistulosa is much lower than in the Acacia/Pseudomyrmex symbiosis. The relatively slow reaction time measured in our experiments with Tetraponera on Barteria likely reflects the low spontaneous patrolling activity of these ants and their weaker reaction to insect herbivory than to mammal herbivory.

Our experiments showed that both ant species, T. latifrons and T. aethiops, reached the leaves more rapidly when these were scraped than when they were undisturbed, demonstrating their response to vibrations. Dejean et al. (2008) already showed that T. aethiops responds to vibration induced by herbivory. However, only T. latifrons responded more strongly to physical damage than to scraping. Behavioural response of T. aethiops did not differ between a scraped and a damaged (thus also vibrated) leaf of its host plant, B. fistulosa, but T. aethiops proved to react more rapidly than T. latifrons in both cases. This difference between the two ants cannot be due to varying levels of spontaneous patrolling, as these did not differ significantly. These results suggest that perception of chemical signals (volatile compounds emitted from the damaged site) improves protection of B. dewevrei by its host ant T. latifrons. Given that damaged leaves were also vibrated by the investigator and that T. aethiops reacts very strongly to scraping, the effect of chemical signals on T. aethiops may have been masked by the effect of scraping in our experimental design. Thus, we cannot conclude on the effect of chemical signalling on T. aethiops. We hypothesize that the responses of T. aethiops to chemical signals and vibration could have evolved to target respectively small insects feeding on the leaves (which are unlikely to induce detectable vibration) and large herbivores such as mammals.

Specificity of ant behavioural response to host plant species

Our study revealed a certain level of specificity in the behavioural response of the two ant species to disturbance of the plant. We showed that both ant species, T. aethiops and T. latifrons, responded more strongly (faster recruitment and more ants recruited) to damage to leaves of their usual host plant species (B. fistulosa and B. dewevrei for T. aethiops and T. latifrons, respectively) than to damage on leaves of the non-host plant species (B. dewevrei and B. fistulosa for T. aethiops and T. latifrons, respectively). As there is a preferential association between T. aethiops and B. fistulosa on the one hand and between T. latifrons and B. dewevrei on the other hand [START_REF] Kokolo | Pattern of specificity in the tripartite symbiosis between Barteria plants, ants and Chaetothyriales fungi[END_REF], specificity of the behavioural response might be a product of ant-plant coevolution within each pair of species. Alternatively, specificity of ant response in the Barteria-Tetraponera system might result from ants acquiring familiarity with the signals of the plant species they presently live on. For instance, arboreal ants have been shown to nest preferentially on plant species to which they have been exposed during development [START_REF] Djiéto-Lordon | Tropical arboreal ant mosaics: innate attraction and imprinting determine nest site selection in dominant ants[END_REF], probably because of a pre-imaginal imprinting process directed on plant odour.

Notwithstanding the specific responses of the ants to damage of their host plant, we showed that T. aethiops responded more strongly to leaf disturbance (scraping and damage), a signal of potential herbivory, than T. latifrons. This difference is expected to translate into better protection conferred by T. aethiops than by T. latifrons.

As the association between T. aethiops and B. fistulosa is more specific than the association between T. latifrons and B. dewevrei [START_REF] Janzen | Protection of Barteria (Passifloraceae) by Pachysima ants (Pseudomyrmecinae) in a Nigerian rainforest[END_REF][START_REF] Kokolo | Pattern of specificity in the tripartite symbiosis between Barteria plants, ants and Chaetothyriales fungi[END_REF], we speculate that the difference in response level might be the result of a tighter coevolution between T. aethiops and B. fistulosa. Tetraponera aethiops and T. latifrons are sister species [START_REF] Ward | Phylogenetic analysis of pseudomyrmecine ants associated with domatia-bearing plants[END_REF] and are the only African species of their species-group [START_REF] Ward | The ant genus Tetraponera in the Afrotropical region: synopsis of species groups and revision of the T. ambigua-group (Hymenoptera: Formicidae)[END_REF]). The differences we observed in their protective behaviour have thus likely evolved after their divergence from a common ancestor that was also in symbiosis with Barteria. This situation is different from those studied by Bruna et al. (2004) and[START_REF] Lapola | Contrasting responses to induction cues by ants inhabiting Maieta guianensis (Melastomataceae)[END_REF], where comparisons involved phylogenetically distant ant species that independently colonized the same plant. The differences between the two species of Tetraponera much more likely reflect coevolution with their Barteria hosts. From a mechanistic point of view, our study demonstrates that these differences are not due to different levels of spontaneous patrolling activity. However, the shorter time lag before reaching the disturbed leaves and the larger number of ants recruited for T. aethiops than for T. latifrons could result from colonies of T. aethiops being larger, leading to more ants involved in defending the plant. It would be worth investigating the level of food rewards provided by the two Barteria species to their ant symbionts to test the hypothesis that B. fistulosa invests more resources into its symbiont to sustain a higher level of protection, and to see whether such a difference has translated into larger, denser colonies of T. aethiops in its host than of T. latifrons in its host.

  Response of T. aethiops to chemical signals should be tested in a vibration-free context. Similar chemical signalling of leaf damage has been demonstrated in many ant-plant symbioses (reviewed in Blatrix & Mayer 2010). Perception of chemical signals indicating herbivory should improve protection efficiency because it allows the ants to locate sites of herbivory quickly and accurately (Agrawal 1998, Gonçalves-Souza 2016, Pacheco & Del Claro 2018). In various myrmecophytic interactions, ant patrolling is focused on young leaves and shoots, even when these are not disturbed (reviewed in Blatrix & Mayer 2010). Such directed patrolling is most likely driven by chemical signalling to provide constitutive protection of the most vulnerable plant parts. Plant chemical signalling of herbivore damage and ant behavioural response to it are expected to coevolve because both partners benefit from deterrence of herbivores.

  1998) Leaf damage and associated cues induce aggressive ant recruitment in a neotropical ant-plant. Ecology 79, 2100-2112. Blatrix R and Mayer V (2010) Communication in ant-plant symbioses. In Baluska F and Ninkovic V (eds.), Plant communication from an ecological perspective. Berlin: Springer, pp. 127-158. Breteler FJ (1999) Barteria Hook. f. (Passifloraceae) revised. Adansonia 21, 306-318. Bruna EM, Lapola DM and Vasconcelos HL (2004) Interspecific variation in the defensive responses of obligate plant-ants: experimental tests and consequences for herbivory. Oecologia 138, 558-565. Chomicki G and Renner SS (2015) Phylogenetics and molecular clocks reveal the repeated evolution of ant-plants after the late Miocene in Africa and the early Miocene in Australasia and the Neotropics. New Phytologist 207, 411-424. Davidson DW and McKey DB (1993) The evolutionary ecology of symbiotic antplant relationships. Journal of Hymenoptera Research 2, 13-83. Dejean A, Djiéto-Lordon C and Orivel J (2008) The plant ant Tetraponera aethiops (Pseudomyrmecinae) protects its host myrmecophyte Barteria fistulosa (Passifloraceae) through aggressiveness and predation. Biological Journal of the Linnean Society 93, 63-69.

Figure caption Figure 1 .

 caption1 Figure caption

Figure 1

 1 Figure 1

Acknowledgements

We thank the Department of Biology of the Université des Sciences et Techniques de Masuku, Franceville (Gabon) for allowing us to perform phytochemical analyses in the Laboratory of Electrophysiology and Pharmacology.

Financial support

This study benefited from funding by the Agence Nationale des Bourses du Gabon (ANBG).


G Sassine

N Najjari

C Brillard

N Defrance

O C Haenssler

D Theron

F Alibart

K Haddadi
email: kamel.haddadi@iemn.univ-lille1.fr

Memristor Device Characterization by Scanning Microwave Microscopy

Keywords: Oxide based random access memory (OxRAM), memristor, scanning microwave microscopy, atomic force microscopy, interferometry, metal oxide semiconductor capacitors

We report memristive device characterization using near-field scanning microwave microscopy. Atomic force microscopy, magnitude and phase-shift images of the complex reflection coefficient of TiO2 devices can be acquired simultaneously in the range 1-20 GHz. In particular, measurement of the complex reflection coefficient of a 200 by 200 nm 2 TiO2 device is exemplary demonstrated. These results are beneficial for electrical modeling and optimization of memristor devices to address OxRAM applications.

I. INTRODUCTION

Resistive random access memory (RRAM) technologies have experienced an increasing interest these last years as a promising solution for storage and memory [START_REF] Torrezan | Sub-nanosecond switching of a tantalum oxide memristor[END_REF]. Indeed, emerging memory devices can offer potential alternative for flash technology or DRAM, thanks to their fast switching performances, high retention and cycling endurance, scalability, and back-end-of-line integration potential. Global understanding of the relative contribution of the different physical mechanisms is very challenging and significant efforts at the modeling and material characterization levels are still needed [START_REF] Sassine | Interfacial versus filamentary resistive switching in TiO2 and HfO2 devices[END_REF].

In this paper, we propose an analysis in the microwave domain to study dynamics in nanometer memristive devices. In particular, we consider TiO2 material that has been largely investigated as prototypical material system for switching. A broadband near-field scanning microwave microscope (NSMM) consisting of an atomic force microscope combined with a vector network analyzer (VNA) is used to study the memristive devices [START_REF] Anlage | Principles of nearfield microwave microscopy[END_REF]. Basically, the tip scans across the sample, emitting a microwave signal scattered by the material, altering its amplitude or/and phase properties [START_REF] Fabiani | Broadband Scanning Microwave Microscopy investigation of graphene[END_REF][START_REF] Gramse | Calibrated complex impedance and permitivity measurements with SMM[END_REF][START_REF]Scanning Microwave Microscopy (SMM) Mode[END_REF][START_REF]Scanning Microwave Impedance Microscopy (sMIM)[END_REF][START_REF] Imtiaz | Near-Field Scanning Microwave Microscopy: An Emerging Research Tool for Nanoscale Metrology[END_REF][START_REF] Haddadi | A 60 GHz scanning near-field microscope with high spatial resolution sub-surface imaging[END_REF]. The measurement setup and device fabrication including dedicated calibration kit are described in Section II. Preliminary experimental results are presented in Section III. In particular, microwave response of the memristive device as a function of the applied bias is demonstrated around 18 GHz.

II. MATERIAL AND METHODS

A. Interferometric SMM setup

The interferometric set-up of the NSMM is depicted in Fig. 1. It consists of a Keysight TM LS5600 AFM interfaced with a Keysight TM PNA series network analyzer E8362B through a homemade tuned interferometric matching network based on the Mach-Zehnder method [START_REF] Dargent | An interferometric scanning microwave microscope and calibration method for sub-fF microwave measurements[END_REF][START_REF] Happy | Measurement techniques for RF nanoelectronic devices : new equipment to overcome the problems of impedance and scale mismatch[END_REF]. This latter is built up in coaxial form with a power divider, two hybrid couplers, an active variable attenuator and two amplifiers in series. The basic principle consists in splitting the PNA source high frequency power wave a1 in two coherent signals, i.e. the reference signal aINC to the AFM tip and the interference signal. The coupler associated to the AFM tip acts as a reflectometer to separate the incident wave aINC and the reflected wave aREF from the device under test (DUT). The wave aREF is then combined with the interference signal to provide the output signal a3 at the output of the second coupler. This signal a3 is cancelled by properly tuning the attenuator to balance the magnitudes of aREF and the interference signal. The resulting signal a3 signal is amplified and measured by the PNA receiver. The resulting measured reflection coefficient Γ = 𝑎 $ 𝑎 % ⁄ considering ideal components can be expressed as a function of the reflection coefficient Γ '() = 𝑎 *+, 𝑎 -./ ⁄ of the DUT by:

Γ = 𝛼(Γ '() + 𝛽) (1)
where 𝛼 is a complex coefficient taken into account losses and phase-shifts introduced by the microwave circuitry and 𝛽 denotes the interference signal. At the test frequency and for a DUT with reference impedance ZREF, the magnitude of the reflection coefficient Γ is set to zero resulting in high measurement sensitivity for impedances around ZREF.

B. OxRAM devices and calibration kit fabrication

TiO2 devices were realized on a P-type silicon substrate of resistivity 1-3 Ωcm (Fig. 2). The devices consist of Ti (5 nm)/Pt (30 nm)/TiO2-x/TiO2/Pt (15 nm)/Au (20 nm) from bottom to top. All metals were deposited by e-beam evaporation, and top electrodes were patterned by electron beam lithography (EBL) with targeted dimensions between 200´200 and 60´60 nm 2 . TiO2-x/TiO2 films were obtained by atomic layer deposition (ALD) at 200°C with TiCl4 as Ti precursor and H2O as oxygen source. The water pulses were set shorter than the ones needed to saturate the surface in order to produce an oxygen deficient TiO2-x layer. Post-deposition oxidation of the TiO2-x top interface into TiO2 was obtained by natural air exposure. An on-wafer calibration kit consisting of MOS capacitors was fabricated on the same wafer. The MOS capacitors are composed of circular gold electrodes evaporated on SiO2 deposited on one part of the wafer (Fig. 3). In order to vary the capacitances values, the diameter of the upper gold pad varies from 0.5 to 2 μm whereas the SiO2 thickness was set to 140 nm. From the AFM image, the topography of the TiO2 devices are extracted along the wafer (Fig. 4). The data indicate a good homogeneity of the fabrication process. The impedance of the MOS structures measured at the tip apex of the probe is modeled by a series model consisting of an oxide capacitance 𝐶 ox and a depletion capacitance 𝐶 depl . Both capacitances can be described by the parallel plate capacitor formalism. The resulting capacitance 𝐶 TOT is given by

𝐶 TOT = 𝐶 ox 𝐶 depl 8𝐶 ox +𝐶 depl 9. ⁄ (2)
The parallel-plate capacitance term 𝐶 ox without taking into account the fringing fields is calculated from the area A of the gold pads and the SiO2 thickness dox:

C ox =A ε < ε rSi0 2 > ox . ( 3
)
The silicon dioxide is assumed to have a relative dielectric constant of ε rSi0 2 = 3.9. The thickness and areas of the capacitors were estimated from the AFM topography measurements (Fig. 3) to take into account any deviation in geometry induced by the fabrication process of the calibration kit. The measured areas A were 1.13 μm 2 , 3.94 μm 2 and 13.85 μm 2 . The charge stored on the capacitor is distributed across a certain depth that adds the depletion series capacitance 𝐶 depl in series to 𝐶 ox . The capacitance was estimated to be proportional to the area A of the metallic electrode and inversely proportional to the depleted zone depth ddepl according to

𝐶 >?@A = 𝐴 C < C DEF > GHIJ , (4)
with 𝑑 >?@A = L2𝜀 O 𝜀 PQR Ψ 𝑞𝑁 V ⁄ and 𝜀 PQR = 12 is the relative permittivity of the silicon bulk substrate, Ψ represents the energy band bending at the Si/SiO2 interface and is set to 200 mV, q is the elementary electron charge (1.6´10 -19 C), 𝑁 V is the doping level of the silicon bulk around 8´10 15 cm -3 . From relations (2) to ( 4), theoretical capacitance data can be derived.

III. EXPERIMENTAL RESULTS

The measurements were performed in contact mode around 18 GHz using a 25PT300A AFM tip from Rocky Mountain Nanotechnology TM . The RF power source is set to -30 dBm and the intermediate frequency bandwidth (IFBW) of the VNA is 100 Hz. The images were scanned over a 20´20 μm 2 with 2048 pixels. In addition to the topography image, the NSMM provides both magnitude and phase-shift images of Γ. Fig. 5 shows the image of the magnitude of the reflection coefficient obtained under zero-bias conditions at f ~ 17.89 GHz. The measurement reliability is influenced by the quality of the electrical contact between tip and sample especially for capacitance gold pads. We observe on some pixels a loss of the contact between the probe and the sample during the scanning. The loss of electrical contact is most likely caused by transient contamination of the gold pads. 200Í200 nm 2 OxRam devices (upper right of the image) are measured with high sensitivity. Magnitude contrast in respect with the background is between 18 and 24 dB. Smallest devices are also very sensitive to the microwave signal but exhibit different responses for devices of same size. A similar phenomenon is observed for the phaseshift of Γ.

Fig. 6 shows the variation of the magnitude and phase of Γ as a function of the DC bias applied between probe tip and the bottom of a 200´200 nm 2 device. From these data, variations of respectively 5 dB and 30 degrees are observed on the measured data when the DC bias is changed from -1.2 to 1.2 V. This is related to the dependence of the device impedance under DC bias.

IV. CONCLUSION

Near-field scanning microwave microscopy measurement of memristive devices have been experimentally demonstrated around 18 GHz. In particular, DC bias voltage impacts both magnitude and phase-shift responses of the microwave reflection coefficient in a sensitive manner. These preliminary results are instructive for further electrical modeling of the device. In particular, future works will include full vector calibration of the devices in a broad frequency range.

Fig. 1 .

 1 Fig. 1. Set-up of the scanning microwave microscope incorporating a tuned interferometric matching network based on the Mach-Zehnder method.

Fig. 2 .

 2 Fig. 2. Configuration of TiO2 devices under the AFM probe.

Fig. 3 .

 3 Fig. 3. AFM topography image of the fabricated sample. On the left, MOS capacitor top electrodes are measured. On the right, the OxRAM stacks are measured.

Fig. 4 .

 4 Fig. 4. 1D topography cross section of the fabricated TiO2 devices from top to bottom of the Fig. 2 image. The size of the OxRAM devices vary from 200´200 down to 60´60 nm 2 .

Fig. 5 .

 5 Fig. 5. Image of the magnitude of the reflection coefficient Γ at f ~ 17.89 GHz.

Fig. 6 .

 6 Fig. 6. Measured magnitude and phase of Γ as a function of the DC bias at f ~ 17.89 GHz.

ACKNOWLEDGMENT

This work is supported by the French National Research Agency (ANR) and German Research Foundation (DFG)project VACSMM. This work used the support of the RENATECH-IEMN for device fabrication. This work used the facilities within the EQPX ExCELSiOR.


Baramee Sakolrak

Rumsais Blatrix

Uthaiwan Sangwanit

Noppol Kobmoo
email: noppol.kob@biotec.or.th

Experimental infection of the ant Polyrhachis furcata with Ophiocordyceps reveals specificity of behavioural manipulation

Keywords: Ophiocordyceps unilateralis sensu lato, Polyrhachis furcata, host-pathogen specificity, behavioural manipulation, experimental infection

Recent studies revealed that fungi of the Ophiocordyceps unilateralis sensu lato complex are highly host-specific. Infected ants leave their colony, wander singly with convulsions and eventually bite firmly vegetal substrates in the low vegetation and maintain this position until death.

Subsequently, a fungal stroma grows from the back of the ant's head and produces spores. We experimentally infected Polyrhachis furcata ants by injecting them with suspensions of blastospores from three closely related fungi of the O. unilateralis species complex: O. polyrhachis-furcata, O. camponoti-leonardi and O. camponoti-saundersi, pathogens isolated from the ant species Polyrachis furcata, Camponotus leonardi and Camponotus saundersi. We monitored the survival and behaviour of ants for 30 d after blastospore injection and compared the results with negative controls. Our results showed that the number of dead ants on the floor did not show significant differences across treatments. However, the typical erratic wandering behaviour and death grip display were observed only when ants were infected by their specific parasite, O. polyrhachis-furcata. Experimental ants initiated death grip between 13 and 17 d after infection, and stayed locked in the position. We suggest that the inability of Ophiocordyceps fungi to manipulate the behaviour of non-host ant species might be responsible for the observed specificity.

The entomopathogenic fungi of the Ophiocordyceps unilateralis species complex are specialized parasites of ants [START_REF] Evans | Cordyceps species and their anamorphs pathogenic on ant (Formicidae) in tropical forest ecosystem. I. The Cephalotes (Myrmycinae) complex[END_REF][START_REF] Evans | Cordyceps species and their anamorphs pathogenic on ants (Formicidae) in tropical forest ecosystems. II. The Camponotus (Formicinae) complex, T. Brit[END_REF]. Production and dispersion of spores rely on modifications of the behaviour of infected ants and count among the most fascinating examples of parasite manipulation of host behaviour, popularly known as the zombie ants' syndrome [START_REF] Oi | Ant behavior and microbial pathogens (Hymenoptera : Formicidae)[END_REF][START_REF] Andersen | The life of a dead ant: The expression of an adaptive extended phenotype[END_REF][START_REF] Hughes | Behavioral mechanisms and morphological symptoms of zombie ants dying from fungal infection[END_REF]. Infected ants singly leave their colony and climb into vegetation by displaying erratic walking and convulsions. They finally bite a vein on the backsides of leaves, the edge of a leaf or a small twig in the low vegetation and die in that position [START_REF] Andersen | The life of a dead ant: The expression of an adaptive extended phenotype[END_REF][START_REF] Pontoppidan | Graveyards on the move: the spatio-temporal distribution of dead Ophiocordyceps-infected ants[END_REF][START_REF] Hughes | Behavioral mechanisms and morphological symptoms of zombie ants dying from fungal infection[END_REF][START_REF] Mongkolsamrit | Life cycle, host range and temporal variation of Ophiocordyceps unilateralis/Hirsutella formicarum on Formicine ants[END_REF]. Thereafter, a stroma emerges from the back of the ant's head and the fungus develops a fruit body and releases spores.

Using experimental infection, de [START_REF] De Bekker | Species-specific ant brain manipulation by a specialized fungal parasite[END_REF] confirmed that the death grip display of two North-American Camponotus species results from infection by Ophiocordyceps.

The O. unilateralis species complex is composed of many species and each one is found growing on different ant species, suggesting host-driven speciation [START_REF] Evans | Hidden diversity behind the zombie-ant fungus Ophiocordyceps unilateralis: four new species described from carpenter ants in Minas Gerais, Brazil[END_REF][START_REF] Luangsa-Ard | Ophiocordyceps halabalaensis: a new species of Ophiocordyceps pathogenic to Camponotus gigas in Hala Bala Wildlife Sanctuary, Southern Thailand[END_REF][START_REF] Kobmoo | Molecular phylogenies reveal host-specific divergence of Ophiocordyceps unilateralis sensu lato following its host ants[END_REF][START_REF] Kobmoo | New species of Ophiocordyceps unilateralis, an ubiquitous pathogen of ants from Thailand[END_REF] [START_REF] Luangsa-Ard | Ophiocordyceps halabalaensis: a new species of Ophiocordyceps pathogenic to Camponotus gigas in Hala Bala Wildlife Sanctuary, Southern Thailand[END_REF][START_REF] Kobmoo | Molecular phylogenies reveal host-specific divergence of Ophiocordyceps unilateralis sensu lato following its host ants[END_REF][START_REF] Kobmoo | New species of Ophiocordyceps unilateralis, an ubiquitous pathogen of ants from Thailand[END_REF]. The mechanisms underlying host-parasite specificity in this system are still unclear. However, experimental injection of hyphae of a North American Ophiocordyceps species into host and non-host ant species showed that the fungus could induce the typical death grip display only in host species [START_REF] De Bekker | Species-specific ant brain manipulation by a specialized fungal parasite[END_REF]. In this study we tested the hypothesis that host specificity of O. unilateralis s. l. species in Thailand arises from the inability of the fungus to manipulate the behaviour of ant species other than its specific host ant species. For this, we infected Polyrhachis furcata ants experimentally for NK257. Ascospore isolation was done within a few hours of collection. Each specimen was fixed to the lid of a Petri dish using petroleum jelly or tape. The lid was placed over the dish filled with Potato Dextrose Agar (PDA) to capture released ascospores on the PDA. Plates were kept in a moist chamber at 20 o C for 2-3 d. The PDA was checked every six hours for discharged ascospores. These were then transferred into Grace's insect cell medium (Gibco® lot no 1294253) [START_REF] Wongsa | Isolation and in vitro cultivation of the insect pathogenic fungus Cordyceps unilateralis[END_REF].

The ascospores developed into blastospores in this medium by budding. A volume of 0.25 ml of this suspension was transferred into 1 ml of Grace's insect cell medium. After blastospores had grown for 3 weeks, 1 ml of suspension was transferred into 25 ml of Grace's insect cell medium and kept in an incubator at 25 0 C for 1 or 2 weeks. The concentration of final stock suspensions for the three fungal species was adjusted to 2.5 x 10 7 spores/ml after measurement using a hemocytometer. The infection was performed by injecting 0.5 μl of blastospore suspension using a Hamilton Gastight Syringe (syringe: Hamilton 7653-01; needle: Hamilton 7803-05) into the thorax underneath the ant's front legs using a stereomicroscope.

For each of the three focal fungal species, beside the injection of blastospores, two other treatments, injection of sterile Grace Medium and no injection, were simultaneously applied each to three replicates of ten ants (i.e. 270 ants in total). The effects of the different fungal species were tested successively at 1 week interval. Each group of ten ants was placed in a plastic box (12 cm x 17 cm x 6.8 cm) containing three artificial small twigs with three leaves each and a shelter composed of a Petri dish covered with aluminium foil. The material was sterilized using 70% ethanol before use to avoid contamination with other fungi. Feeding and laboratory conditions were the same as described above. The numbers of living ants, ants displaying death grip and dead ants on the box floor were recorded every day for 30 d. At the end of the experiment, all dead ants were kept, both those dead on the floor and those displaying death grip, in order to monitor the fungal development from the ants' body for one month. Fungal growth out of the ant's body was not observed. Moisture was then increased as this is an important requirement for fungal growth; two cotton balls saturated with water were put in the boxes and supplied with water everyday. However, opportunistic fungi such as Penicillium spp. and Aspergillus spp. quickly covered the dead ants, precluding the use of DNA sequencing for confirming the fungal species present inside the cadavers.

Several ants were found dead on the first day of the experiment, in particular in the groups that were injected (either with Grace Medium or with an inoculum). The injection procedure, and not the inoculum, was likely to be responsible for early death. Durting the first 15 d, the number of dead ants on the floor was lower for the control with no injection than for the two other treatmentsinjection of Grace Medium and of the inoculum-and was similar for these two treatments, and for all the three O. unilateralis species tested (Supplementary Table 1). After 15 d of experiment, the number of dead ants on the floor tended to increase for the ants injected with the inoculum, in particular when injected with O. camponoti-saundersi (Fig. 1), suggesting a possible negative effect of the inoculum on the survival of the ants.

Interestingly, the only treatment that induced death grip was the infection with O. polyrhachis-furcata, the specific O. unilateralis species of P. furcata (Fig. 1). The death grip occurred 13 d after inoculation and increased in number of ants until 17 d after inoculation, then remained stable. This treatment also induced the typical wandering behaviour with convulsions (Fig. 1 and Supplementary material), while biting an artificial leaf, similar to the behaviour observed in the field in ants naturally infected by the O. unilateralis s. l. species. Such behaviour was not observed in the other treatments. Our results show that among the three entomopathogenic fungi tested, only the pathogen of P. furcata ants was successful in manipulating the behaviour of this ant species, although

  with three fungal species of O. unilateralis s. l., i.e. O. polyrhachis-furcata, O. camponoti-saundersi and O. camponoti-leonardi, and recorded the ant behaviour. One colony of P. furcata was collected in Khao Yai National Park, Thailand, and reared in the laboratory at the National Center for Genetic Engineering and Biotechnology (BIOTEC), Pathum Thani, under 25 o C, 40-55 % moisture and 10 h exposure to neon light. Ants were fed every 2 d with 15 % honey agar (distilled water 85 ml; honey 15 ml; agar 1.5 g) and were provided a cotton ball saturated with water. They were kept in the lab for one month before experiments to acclimatize to laboratory conditions. One of each of three fungal species, O. polyrhachis-furcata (NK 298), O. camponoti-leonardi (NK 257) and O. camponoti-saundersi (NK 270) containing mature perithecia was collected in Khao Yai National Park for NK 298 and NK 270, and in the Wiang Pa Pao district, Chiang Rai province,

Figure

  Figure Caption:

Figure 1 :

 1 Figure 1: Number of ants dead on the floor (DF) or displaying death grip (DG) during 30 d after injection of blastospores of Ophiocordyceps polyrhachis-furcata (blue), O. camponoti-saundersi (red) or O. camponoti-leonardi (black). The picture shows a Polyrhachis furcata ant displaying death grip on an artificial leaf.

  . Morphological and molecular studies of Ophiocordyceps

	unilateralis in Thailand revealed six fungal species, namely O. polyrhachis-furcata, O. camponoti-
	saundersi, O. camponoti-leonardi, O. halabalaensis, O. septa and O. rami, parasitizing the ant species
	Polyrhachis furcata, Colobopsis saundersi, C. leonardi, Dinomyrmex gigas, Camponotus sp.1 and
	Camponotus sp.2, respectively

Acknowledgements

This research was funded by an International Program for Scientific Cooperation (PICS n°6453) of the National Center for Scientific Research (CNRS) to RB and NK, by the National Center for Genetic Engineering and Biotechnology (BIOTEC), Pathum Thani and by the Higher Education Research Promotion and National Research University Project of Thailand, Office of the Higher Education Commission (NRU): Kasetsart University-Thailand. The sampling of ants and fungi were authorized by the Department of National Parks, Wildlife and Plant Conservation (DNP) of Thailand.

We would like to thank Nuntanat Arnarmnart for the preparation the fungal inoculum.

the three fungi are closely related [START_REF] Kobmoo | Molecular phylogenies reveal host-specific divergence of Ophiocordyceps unilateralis sensu lato following its host ants[END_REF]. This is consistent with de Bekker et al. (2014) in which experimental infection of ant species with an O. unilateralis s. l. species from North America would only induce wandering walking and death grip on the fungus's specific host ant species.

Previous attempts to infect ants by spraying spores on the ants' body were unsuccessful (personal data). Our latest results, obtained for the first time in a tropical Southeast Asian region and in accordance with the evidence from North America (de Bekker et al. 2014) suggest that the inability of Ophiocordyceps fungi to manipulate the behaviour of non-host ant species might be responsible for the observed specificity throughout the distribution area of O. unilateralis group. When various hostparasite species pairs occur in syntopy, as is the case for the three focal pairs targeted in our studies [START_REF] Kobmoo | Molecular phylogenies reveal host-specific divergence of Ophiocordyceps unilateralis sensu lato following its host ants[END_REF], it is likely that non-host ant species would be infected by each Ophiocordyceps species but would represent a dead-end for the development of the fungus. In conclusion, the specificity between O. unilateralis s. l. fungi and their ant hosts does not rely on the evolution of chemical defences by ants at the cuticle level but involves the mechanism underlying host behaviour manipulation by the parasite inside the ants' body. A specific match between the metabolites produced by the fungus within the ant's body and the functioning of the nervous system of the ant is certainly the key for a successful infection [START_REF] De Bekker | Species-specific ant brain manipulation by a specialized fungal parasite[END_REF]).


Lamine Diamé
email: diamelamine99@gmail.com

Brian Taylor
email: dr.brian.taylor@ntlworld.com

Rumsaïs Blatrix
email: rumsais.blatrix@cefe.cnrs.fr

Jean-François Vayssières
email: jean-francois.vayssieres@cirad.fr

Jean-Yves Rey
email: jeanyvesp.rey@gmail.com

Isabelle Grechi
email: isabelle.grechi@cirad.fr

Karamoko Diarra
email: karamoko.diarra@ucad.edu.sn

A preliminary checklist of the ant (Hymenoptera, Formicidae) fauna of Senegal

Keywords: ants, checklist, new records, sub-Saharan country, Senegal

This work presents the first checklist of the ant species of Senegal, based on a review of the literature and on recent thorough sampling in Senegalese orchard agrosystems during rainy and dry seasons. Eighty-nine species belonging to 31 genera and 9 subfamilies of Formicidae are known. The most speciose genera were Monomorium Mayr, 1855, and Camponotus Mayr, 1861, with 13 and 12 species, respectively. The fresh collection yielded 31 species recorded for the first time in Senegal, including two undescribed species. The composition of the ant fauna reflects the fact that Senegal is in intermediate ecozone between North Africa and sub-Saharan areas, with some species previously known only from distant locations, such as Sudan.

Introduction

Information on the ant fauna of Senegal is mostly known from scattered historical records, and no synthetic list has been published. The first record dates from 1793 while the most recent was in 1987 (see Table 1). Presence data can also be deduced from papers studying the ecology and/or the behaviour of some ant species [START_REF] Agbogba | Observations on the feeding-preparation signals of larvae in the ponerine ant Pachycondyla caffraria (Smith)[END_REF][START_REF] Agbogba | Settlement in the prey termite nest by the ponerine ant Pachycondyla caffraria (Smith), and tandem running signal analysis for the following ant[END_REF][START_REF] Agbogba | Division of labour between foraging workers of the ponerine ant Pachycondyla caffraria (Smith) (Hymenoptera: Formicidae)[END_REF][START_REF] Gillon | Production et consommation de graines en milieu sahelo-soudanien au Senegal: les fourmis, Messor galla[END_REF]. Other have reported the participation of ant species in the diet of animals such as Chimpanzees [START_REF] Bogart | Insectivory of Savanna Chimpanzees (Pan troglodytes verus) at Fongoli, Senegal[END_REF][START_REF] Mcgrew | Chimpanzees use tools to harvest social insects at Fongoli, Senegal[END_REF].

The two Senegalese agroecosystems known as the "Niayes": (Mboro, Noto and Ndoyène localities in the maps) and "Plateau de Thiès": (Thiès, Pout and Sindia localities in the maps) (Fig. 1) represent two major fruit and vegetable production areas in Senegal. Plant diseases and damage caused by fruit flies are becoming common to these two agroecosystems [START_REF] Diatta | Fruit phenology of citruses, mangoes and papayas influences egg-laying preferences of Bactrocera invadens (Diptera: Tephritidae)[END_REF][START_REF] Diamé | Influence of Oecophylla longinoda Latreille, 1802 (Hymenoptera: Formicidae) on mango infestation by Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) in relation to Senegalese orchard design and management practices[END_REF]. Ants are important components of ecosystems [START_REF] Hölldobler | The ants[END_REF][START_REF] Passera | Les fourmis: Comportement, organisation sociale et évolution[END_REF] and are even considered as ecosystem engineers [START_REF] Folgarait | Ant biodiversity and its relationship to ecosystem functioning: a review[END_REF]. Because of their predatory behaviour, ants can be helpful auxiliaries in pest control [START_REF] Philpott | Biodiversity in tropical agroforests and the ecological role of ants and ant diversity in predatory function[END_REF][START_REF] Van Mele | Effects of an African weaver ant, Oecophylla longinoda, in controlling mango fruit flies (Diptera: Tephritidae) in Benin[END_REF][START_REF] Dwomoh | Investigations Oecophylla longinoda Latreille (Hymenoptera: Formicidae) as a biocontrol agent in the protection of cashew plantations[END_REF]. A meta-analysis of studies in agroecosystems has found that generalist predators (single-and multiple-species assemblages) controlled herbivore abundance (79% of studies) and reduced plant damage and increased plant yields (65% of studies) [START_REF] Symondson | Can generalist predators be effective biocontrol agents?[END_REF].

A detailed description of the ant fauna of the "Niayes" and "Plateau de Thiès" agroecosystems has thus been undertaken, and might usefully improve the current scattered knowledge of the ant fauna of Senegal. Actually, there are already some regional treatments of ant faunas in Africa. For instance, in the last decades, several works have been undertaken in many parts Africa including countries such as Ghana [START_REF] Belshaw | The effect of forest disturbance on the leaf litter ant fauna in Ghana[END_REF], Nigeria [START_REF] Taylor | The ant mosaic on cocoa and other tree crops in Western Nigeria[END_REF], Tanzania [START_REF] Robertson | Ants (Hymenoptera: Formicidae) of Mkomazi. In: Mkomazi: the ecology, biodiversity and conservation of a Tanzanian savanna[END_REF], Gabon [START_REF] Fisher | Diversity Patterns of Ants (Hymenoptera: Formicidae) Along an Elevational Gradient on Monts Doudou in Southwestern Gabon[END_REF]), Kenya (Hita Garcia et al. 2009, 2013), Cameroon [START_REF] Deblauwe | Diversity and distribution of ground-dwelling ants in a lowland rainforest in southeast Cameroon[END_REF]. Since a more complete inventory of African ants is needed and even essential to advance understanding their distribution throughout Africa and take full advantage of their demonstrated value, this paper presents a more recent list of the ant species of Senegal based on a review of the literature and on material we collected in the "Niayes" and "Plateau de Thiès" orchard agroecosystems.

Senegal is an African western country with an arid climate generated by the sudano-sahelian climatic conditions that occur in that part of the continent. It is mainly a low-lying country, with a semi-desert area in the north and northeast and forests in the southwest. The largest rivers include "The Senegal" in the north and "The Casamance" in the southern tropical climate region.

Methods

Our literature review is based on historical taxonomy papers as well as other antrelated papers. A large part of this literature review, as well as additional data, was available from the second author's web site on the ants of Africa (Taylor, 2014a). The new investigations were conducted in orchard agroecosystems of the "Niayes" and "Plateau de Thiès". These regions are characterized by ferralic arenosols and a sudano-sahelian climate with unimodal rainfall from July to September. Although climate is sudano-sahelian for these agroecosystem zones, temperatures are lowest in the west, especially in the northern coast than in the center of the country. For instance, the 'Niayes" localities benefit to winds ocean influence that permit them to record more longer low temperatures than localities of 'Plateau de Thiès'(Fig. 1).

Ants were sampled in 51 orchards in 2012, during both the dry and rainy seasons, using pitfall traps (40 in each orchard) distributed on the ground over all microhabitats (sun exposed habitats, shaded habitats and hedges), hand collection (on ground, tree trunks, dead woods etc) and dietary baits (tuna fish). There was no specific period of the ant sampling in the month. The pitfall traps were placed randomly in order to last 48 hours in the orchard before we completed the survey the day of picking up the traps. Ants were placed in plastic vials filled with 80° alcohol. Once in the laboratory, each sample was sorted and the specimens classified into morphospecies. Specimens of each morphospecies were examined and identified by Dr Brian Taylor. The original specimens as mounted and identified by Brian Taylor are held by him and will be deposited in the Oxford University Museum of Natural History (Taylor, 2014b). The species list (Table 1) is arranged in alphabetic order by subfamily, genus and species. The nomenclature largely follows the Bolton online catalogue of the ants of the world (AntCat) (Taylor, 2014c). In most cases, type images are available online from the Antweb.org project of the California Academy of Sciences.

Results

The ant species list of Senegal (Table 1) contains 89 described species. Two among them are undescribed and new to science. They belong to the genera Monomorium Mayr, 1855 andTetramorium Mayr, 1855. The 89 species are distributed across 31 genera belonging to 9 subfamilies which are: Aenictinae, Amblyoponinae, Cerapachyinae, Dolichoderinae, Diamé. Record extends known range right across from Ethiopia and Eritrea. Ground-nesting ant. Dufour, 1862, Sindia (14°34'53.84''N;17°02'24.52''W -30m), 20.II.2012;Thies (14°47'22.16''N;16°57'57.16''W -78m), 28.VII.2012 collect. L. Diamé.

Cataglyphis savignyi

Record extends known range right from Egypt and Tunisia. Ground-nesting ant.

Cerapachys noctambulus (Santschi, 1910), Peyckouk (14°45'35.02''N;16°52'56.19''W -59m), 12.VIII.2012;Sindia (14°34'53.84''N;17°02'24.52''W -30m) André, 1884, Pout (14°45'28.14''N;17°03'02.78W -36m), 06.VIII.2012;Thies (14°47'22.16''N;16°57'57.16''W -78m), 28.VII.2012, collect. L.

Meranoplus magrettii

Diamé. Record adds to known range of a pan-African species. Ground nesting ant. Santschi, 1915, Sindia (14°34'54.52''N;17°02'23.12''W -30m), 20.II.2012; Pout (14°45'N; 17°03W -37m), 21.V.2012, collect. L. Diamé. Record is a suprising extension of the range of a species otherwise known only from Kenya, although M.J. Lush (pers.comm.) has collected it from Gambia. Possibly due to human transportation.

Monomorium osiridis

Ground foraging and probably nesting.

Monomorium salomonis (Linnaeus, 1758), Notto (14°58'54.28''N;17°00'26.19W -31m), 22.VI.2012;Thies (14°47'22.16''N;16°57'57.16''W -78m), 28.VII.2012, collect. L. Diamé.

Record adds to the known range of an essentially North African species. Ground nesting ant. Bolton, 1987, Pout (14°45'35.95''N;17°03'23.58 (Forel, 1902)], Ndoyenne (14°47'54.14''N; 17°08'30.99''W -45m), 24.V.2012, collect. L. Diamé. Santschi, 1930, Pout (14°45'30.12''N;17°03'26.81''W -34m) Taylor has other specimens from Benin. Probably ground nesting but known to forage on plants.

Monomorium vonatu

Pheidole andrieui

Tapinolepis simulans (Santschi, 1908), Thies (14°47'03.12''N; 16°58'02.10''W -84m), Tapinoma demissum Bolton, 1995, Pout (14°45'13.62 [START_REF] Bolton | Taxonomy of the dolichoderine ant genus Technomyrmex Mayr (Hymenoptera: Formicidae) based on the worker cast[END_REF].

Tetramorium angulinode Santschi, 1910, Pout (14°45'21.30''N;17°03'14.35 [START_REF] Bolton | The ant tribe Tetramoriini (Hymenoptera: Formicidae). Constituent genera, review of smaller genera and revision of Triglyphothrix Forel[END_REF].

Tetramorium simillimum F Smith, 1851, Ndoyenne (14°45'38.85''N; 17°08'51.95W -44m), 24.V.2012, collect. L. Diamé. Widely distributed tramp species. Ground and tree crevice nesting known to forage on plants.

The two undescribed species:

Monomorium sp, Pout (14°45'30.12''N; 17°03'26.81''W -34m), 21.VII.2012; Thies (14°47'22.16''N; 16°57'57.16''W -78m), 28.VII.2012, collect. L. Diamé, det. B. Taylor.

Image:

http://antsofafrica.org/ant_species_2012/monomorium/monomorium_nsp_diame_senegal/ monomorium_nsp_diame_senegal.htm.

Tetramorium species, Pout (14°45'30.12''N; 17°03'26.81''W -34m), 21.VII.2012; Thies (14°47'03.12''N; 16°58'02.10''W -84m), 28.VII.2012, collect. L. Diamé, det. B. Taylor. This may be a species of Temnothorax but differs from the described members of that genus, notably the large-eyed T. megalops (Hamann & Klein, 1967) and T. barryi (Cagniant, 1967) from Algeria. It also has distinct frontal carinae, expressly stated by [START_REF] Bolton | Synopsis and classification of Formicidae[END_REF] as absent in Temnothorax species.

Image: http://antsofafrica.org/ant_species_2012/tetramorium/tetramorium_nsp_diame_senegal/ tetramorium_nsp_diame_senegal.htm.

Discussion

With 89 species recorded, the ant fauna of Senegal can be considered as relatively diverse compared to the other neighbouring Sahelian countries such as Mali, or Niger, where 33 and 10 species respectively are now known (Taylor website), especially in view of the size of the country and that several important zones were not investigated. In particular, samples collected in the fruit-based agroecosystems from the "Niayes" and "Plateau de Thiès" regions show a high relative ant diversity. The climatic preferences of the species listed in this paper show Senegal to be an intermediate ecozone between North Africa and the sub-Sahara area.

Our results show additions to the published ranges about Sahelian ant faunas and probably semi-arid ant species across sub-Saharan Africa.

Ants may be useful auxiliaries in pest management because of the many relationships they have with other components of ecosystems. Using ants for biological control has gained some ground over the last 10 years in Africa, due to the intensification of damage by fruit flies since the arrival of Bactrocera dorsalis (Hendel) in the western part of the African continent. The knowledge of the ant diversity in underlined agroecosystems may prove useful for developing sustainable pest management programs. For instance, ant species such as Oecophylla longinoda for mango and Citrus fruit flies [START_REF] Van Mele | Effects of an African weaver ant, Oecophylla longinoda, in controlling mango fruit flies (Diptera: Tephritidae) in Benin[END_REF][START_REF] Sinzogan | Implications of on-farm research for local knowledge related to fruit flies and the weaver ant Oecophylla longinoda in mango production[END_REF], Pachycondyla analis [START_REF] Latreille | Histoire Naturelle des Fourmis, et recueil de mémoires et d'observations sur les abeilles, les araignées, les faucheurs, et autres insectes[END_REF]) (now revised to Megaponera analis [START_REF] Latreille | Histoire Naturelle des Fourmis, et recueil de mémoires et d'observations sur les abeilles, les araignées, les faucheurs, et autres insectes[END_REF]) against termites pests [START_REF] Yusuf | An Effective Method for Maintaining the African Termite-Raiding Ant Pachycondyla analis in the Laboratory[END_REF]Yusuf et al. 2014) can be suitable biocontrol agents into developed IPM (Integrated Pest Management) programs in view of the problems generated by flies and termites in such agroecosystems. However, some ant species can be suspected as possible problematic species for crops in the orchards. The species Pheidole megacephala for instance, has been indexed to make a strong competition for occupation the canopy with O. longinida, a biological control agent against fruit flies [START_REF] Seguni | The effect of ground vegetation management on competition between the ants Oecophylla longinoda and Pheidole megacephala and implications for conservation biological control[END_REF]. [START_REF] Diame | Relations between the design and management of Senegalese orchards and ant diversity and community composition[END_REF] showed also that Monomorium salomonis which is highly anthropophile, is the dominant ant species in certain orchards. Its dominance among other species makes it susceptible to rear crop pests such as Coccidae scale insects.

It is likely that the total number of ant species for Senegal is actually higher since our collection campaigns concerned only the western part of the country crossing Saint-Louis, Thies, Dakar and Casamance regions. First, just the survey in the orchard agroecosystems of the "Niayes" and "Plateau de Thiès" in 2012 revealed 29 species new to Senegal, i.e. about one third of the published ant fauna of Senegal. Similar sampling efforts conducted in other localities such as Ferlo, Djolof, Sine Saloum or Niokolo Koba ecosystems could detect many additional species. For instance,the richness of the Ponerinae subfamily in Guinean ant fauna (48 species), Ivory Coast ant fauna (36 species) or Ghana ant fauna (58 species), suggests this should be richer for Senegal if intensive sampling was carried out in forested landscape located in the south part of country as well as Casamance region. Second, from north to south, the country is crossed by four vegetation types induced by the Sahel, the Sudano-sahelian Savannah, the Sudan Savannah and the south Guinea Savannah climates which can promote various ant fauna. Indeed, ant community composition and diversity vary according to climatic zones. For instance, energy-speciation induced by available local resources [START_REF] Kaspari | Energy gradients and the geographic distribution of local ant diversity[END_REF], the gradient of the altitude and latitude [START_REF] Ward | Broad-Scale Patterns of Diversity in Leaf Litter Ant Communities[END_REF] or the sea level [START_REF] Lach | Synthesis and Perspectives[END_REF]) are geographic parameters often indexed as influencing ant fauna.

  , 20.II.2012; Ndoyenne (14°45'09.95''N; 17°03'43.49''W -48m), 21.VI.2012; collect. L. Diamé. First record outside Tunisia and Egypt. Probably a ground nesting ant. Crematogaster (Cr.) brunneipennis André, 1890, Ndoyenne (14°45'09.95''N; 17°03'43.49''W -48m), 21.VI.2012, collect. L. Diamé. Record extends known range north from Senegal. Arboreal nesting ant. Dorylus (D.) aegyptiacus Mayr, 1865, stat.rev., Pout sigelec (14°45'40.38''N; 17°02'25.40''W -43m), 21.VI.2012; Ndoyenne (14°45'09.95''N; 17°03'43.49''W -48m), 21.VI.2012, collect. L. Diamé, media workers collected. Regarded here as meriting revived status. Record extends known range right across from Egypt, Sudan and Ethiopia. Groundnesting ant. Lepisiota acholli Weber, 1943, Ndoyenne (14°46'05.25''N; 17°09'04.54''W -50m), 07.IV.2012; Thies (14°47'22.16''N; 16°57'57.16''W -78m), 28.VII.2012, collect. L. Diamé. Record extends published range from South Sudan, although B. Taylor has specimens from right across the Sahel. Probably ground nesting but known to forage on plants.

  28.VII.2012; Peyckouk (14°45'35.02''N; 16°52'56.19''W -59m), 12.VIII.2012, collect. L.Diamé. Sole prior records are from Tunisia and Algeria, although B. Taylor has a specimen from Sudan. Ground-nesting desert species.

  Yusuf A.A., Gordon I., Crewe R.M., Pirk C.W.W. 2014. Prey choice and raiding behaviour of the Ponerine ant Pachycondyla analis (Hymenoptera: Formicidae). Journal of Natural History 48: 5-6, 345-358. DOI: 10.1080/00222933.2013.791931.

Figure 1 :

 1 Figure 1: Maps presenting Senegal in West Africa (topright), the "Niayes": (Mboro, Noto and Ndoyène localities) and "Plateau de Thiès": (Thiès, Pout and Sindia localities), two agroecosystems zones in Senegal where fresh collection of ants was carried out (topleft), and the averages of annual rainfall (middle) and annual temperatures (bottom) in the country (source: Sagna & Leroux, 2000).

  Diamé. Sole prior record is from the type location in Ghana. Ground foraging and probably nesting.

	Monomorium sp. undet. [Trichomyrmex mayri

''W -34m), 21.VII.2012; Thies (14°47'22.16''N; 16°57'57.16''W -78m), 28.VII.2012, collect. L.

  Record extends published range from Mali, although B. Taylor has specimens from right across the Sahel. Probably ground nesting but likely to forage on plants. Record extends published range from DRCongo, although B. Taylor has other specimens from Senegal and Benin. Ground nesting ant. 16°52'56.19''W -59m), 12.VIII.2012, collect. L. Diamé, major and minor workers collected. Otherwise recorded only from the type location in Guinea. Probable ground nesting ant. VI.2012, collect. L. Diamé, minor workers collected. Regarded here as meriting species status, elevated from a stirps or subspecies of Pheidole sculpturata Mayr, 1886. Record extends known range from DRCongo west through Ivory Coast and Guinea. Ground-nesting species. VII.2012, collect. L. Diamé. Record extends published range from Sudan, although B.

	,
	21.VII.2012; Thies (14°47'03.77''N; 16°58'04.41''W -84m), 20.IV.2012, collect. L. Diamé,
	minor workers collected. Pheidole bequaerti Forel, 1913, Ndoyenne, (14°46'22.08''N; 17°03'49.90''W -45m),
	21.VI.2012; Thies (14°47'03.77''N; 16°58'04.41''W -84m), 20.IV.2012; Pout
	(14°45'28.14''N; 17°03'02.78W -36m), 06.VIII.2012, collect. L. Diamé, minor workers
	collected. Pheidole mentita Santschi, 1914, Sindia (14°34'23.13''N; 17°02'17.44''W -30m),
	20.II.2013; Thies (14°47'03.77''N; 16°58'04.41''W -84m), 20.IV.2012; Peyckouk
	(14°45'35.02''N; Pheidole welgelegenensis Forel, 1913, stat.rev., Thies (14°47'03.77''N; 16°58'04.41''W -
	84m), 20.IV.2012; Ndoyenne, (14°46'22.08''N; 17°03'49.90''W -45m), 21.VI.2012; Pout
	(14°45'30.12''N; 17°03'26.81''W -34m), 21.VII.2012; Thies (14°47'03.77''N;
	16°58'04.41''W -84m), 20.IV.2012; Notto (14°58'54.28''N; 17°00'26.19W -31m),
	22.Tapinolepis pernix (Viehmeyer, 1923), Thies (14°47'22.16''N; 16°57'57.16''W -78m),
	28.

  ''N; 17°03'07.71''W -38m), 26.IV.2012; Thies (14°47'22.16''N; 16°57'57.16''W -78m), 28.VII.2012, collect. L. Diamé. Sole prior published records are from Zimbabwe, although B. Taylor has a specimen from Tanzania. Ground-nesting ant.Technomyrmex senexBolton, 2007, Notto (14°56'26.62''N; 17°01'31.66W -23m), 18.VI.2012, collect. L. Diamé. Prior records from Ghana and the Congo Basin, a leaf litter inhabiter

	Tapinoma melanocephalum (Fabricius, 1793), Ndoyenne (14°46"18.15''N; 17°03'44.90''W
	-47m), 07.IV.2012; Thies (14°47'22.16''N; 16°57'57.16''W -78m), 28.VII.2012, collect. L.
	Diamé. Commonly recorded as a pan-tropical tramp species. Forages on ground and in
	buildings, nesting in crevices.

  ''W -35m), 08.V.2012; Thies (14°47'22.16''N; 16°57'57.16''W -78m), 28.VII.2012, collect. L. Diamé.Record adds to known range of a pan-African species. Nests among roots of grasses and low plants.

	Tetramorium muscorum Arnold, 1926, Pout sigelec (14°45'52.52''N; 17°02'49.36W -40m),
	27.IV.2012; Thies (14°47'22.16''N; 16°57'57.16''W -78m), 28.VII.2012, collect. L. Diamé.
	Record adds to known range of a pan-African forest species.
	Tetramorium rothschildi Forel, 1907, Notto (14°58'12.42''N; 17°01'27.28W -29m),
	18.VI.2012; Pout (14°45'21.30''N; 17°03'14.35''W -35m), 08.V.2012; Thies
	(14°47'22.16''N; 16°57'57.16''W -78m), 28.VII.2012, collect. L. Diamé. Record adds to
	known range from Ethiopia, Kenya and Ghana, in dry or semi-desert areas

Table 1 :

 1 Checklist of the ant species of Senegal. The list is arranged alphabetically by subfamily, genus and species. Names in bold refer to species recorded in Senegal for the first time. Species with an asterisk have been recorded in our survey of orchard agroecosystems in the "Niayes" and "Plateau de Thiès".Note: Unless no type images are available, which mainly applies to very early descriptions, all specimens collected by the authors have been checked against the type photographs on Antweb. It needs to be recognised that the Antweb images almost always have a prevalent magenta tint and the apparent colours may vary from the type descriptions.

	Subfamilies	Scientific valid name, author descriptor and	References of collection	Checked and type images:
		year of species description	or the last report of the	e.g AntwebCASENT+code
			species in Senegal		number
	AENICTINAE	Aenictus furculatus Santschi, 1919	Santschi (1920a)		Type location Senegal;
						CASENT0911425
		Aenictus fuscovarius Gerstäcker, 1859	Wheeler	(1922);	as	Type location Mozambique;
			Aenictus fuscovarius ssp	no type images; magrettii,
			magrettii			CASENT0903755, from
						Sudan
		Aenictus humeralis Santschi, 1910	Santschi (1910); as ssp	Type damaged, see
			chevalieri			subspecies (male)
						chevalieri,
						CASENT0911429, from
						Senegal
		Aenictus soudanicus Santschi, 1910	Santschi (1913)		Type location Mali, male,
						CASENT0911441
	AMBLYOPONINAE	Stigmatomma santschii Menozzi, 1922	Menozzi (1922); genus	Type location Senegal; no
			revived by Yoshimura &	type images; type not
			Fisher (2012)		obviously sighted by
						Yoshimura & Fisher (2012)
	CERAPACHYINAE	*Cerapachys noctambulus (Santschi, 1910)				Type location Tunisia; first
						record of the worker morph;

Acknowledgments

We would like to thank PDMAS (Programme de Développement des Marchés Agricoles du Sénégal) which supported the financial part of this work. Thanks are also dedicated to Hubert de Bon (CIRAD-UPR HortSys) for all professional contacts he initiated and all financial issues he undertook for the article. We are grateful to Annie Boyer (CIRAD-Dist) for his help about bibliographic research related to the published ants for Senegal. We thank the orchard owners for allowing us to conduct this survey in good conditions and for help in fields work.

*Lepisiota acholli

 (Weber, 1943)Type location South Sudan, CASENT0903162 Lepisiota canescens (Emery, 1897) Santschi (1914) Type location Somalia, CASENT0905153 Lepisiota capensis [START_REF] Mayr | Myrmecologische Studien[END_REF] Mayr (1895), this may have been a misidentification as verifiable records appear to be from south of the Equator Type location South Africa, CASENT0915714. Note the dark erect hairs *Lepisiota laevis [START_REF] Santschi | Glanure de fourmis africaines[END_REF] revived status [START_REF] Santschi | Glanure de fourmis africaines[END_REF] Type location Senegal; CASENT0912373 *Oecophylla longinoda [START_REF] Latreille | Histoire Naturelle des Fourmis, et recueil de mémoires et d'observations sur les abeilles, les araignées, les faucheurs, et autres insectes[END_REF] Santschi (1914) Type location Sierra Leone; no type images of major worker; minor described as Oecophylla brevinodis André, 1890, CASENT0913754 *Paratrechina longicornis [START_REF] Latreille | Histoire Naturelle des Fourmis, et recueil de mémoires et d'observations sur les abeilles, les araignées, les faucheurs, et autres insectes[END_REF] [START_REF] Latreille | Histoire Naturelle des Fourmis, et recueil de mémoires et d'observations sur les abeilles, les araignées, les faucheurs, et autres insectes[END_REF] Type location Senegal; no type images; well recognised tramp species Paratrechina subtilis (Santschi, 1920) Santschi (1920b) Type location Senegal, CASENT0912308 *Tapinolepis simulans (Santschi, 1908) Type location Tunisia, CASENT0912357 *Tapinolepis pernix (Viehmeyer, 1923) Type location Sudan, (Antweb) FOCOL2894 MYRMICINAE Atopomyrmex mocquerysi [START_REF] André | Hyménoptères nouveaux appartenant au groupe des formicidés[END_REF][START_REF] André | Hyménoptères nouveaux appartenant au groupe des formicidés[END_REF] Type location Senegal, CASENT0101460 Carebara sicheli [START_REF] Mayr | Myrmecologische Studien[END_REF][START_REF] Mayr | Myrmecologische Studien[END_REF] Type location Senegal, CASENT0919628 (queen) Carebara silvestrii [START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF][START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF] Type location Guinea, specimens labelled type by Santschi are not from Guinea but Ghana, e.g. CASENT0913522 *Cardiocondyla emeryi Forel, 1881 Type location Virgin Is., tramp species, CASENT0101216 *Crematogaster brunneipennis [START_REF] André | Matériaux pour servir à la faune myrmécologique de Sierra Leone (Afrique occidentale)[END_REF] Type location Sierra Leone, CASENT0902089 *Crematogaster censor [START_REF] Forel | Note sur quelques fourmis d'Afrique[END_REF][START_REF] Forel | Note sur quelques fourmis d'Afrique[END_REF] Type location Senegal, CASENT0908511 Crematogaster coelestis Santschi, 1911[START_REF] Santschi | Résultats scientifiques des croisières du Navire-École Belge "Mercator." 2. Formicidae[END_REF] Type location Senegal, CASENT0912662 Crematogaster depressa [START_REF] Latreille | Histoire Naturelle des Fourmis, et recueil de mémoires et d'observations sur les abeilles, les araignées, les faucheurs, et autres insectes[END_REF][START_REF] Mayr | Afrikanische ormiciden[END_REF] Type location Guinea, no type images; ssp fuscipennis, CASENT0904471 *Crematogaster kneri [START_REF] Mayr | Myrmecologische Studien[END_REF][START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF] Type location Ghana, CASENT0919670 *Crematogaster senegalensis [START_REF] Roger | Die neu aufgeführten Gattungen und Arten meines Formiciden-Verzeichnisses, nebst Ergänzung einiger früher gegeben Beschreibungen[END_REF][START_REF] Roger | Die neu aufgeführten Gattungen und Arten meines Formiciden-Verzeichnisses, nebst Ergänzung einiger früher gegeben Beschreibungen[END_REF] Type location Senegal, no type images; ssp devincta, CASENT0912722 Melissotarsus emeryi Forel, 1907[START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF] Type location Ethiopia, CASENT0101465 *Meranoplus magrettii André, 1884 Type location Sudan, CASENT0915400 *Messor galla (Mayr, 1904) [START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF], [START_REF] Bolton | Afrotropical species of the Myrmicine ant genera Cardiocondyla, Leptothorax, Melissotarsus, Messor and Cataulacus (Formicidae). Bulletin of the British Museum (Natural History)[END_REF]; [START_REF] Gillon | Production et consommation de graines en milieu sahelo-soudanien au Senegal: les fourmis, Messor galla[END_REF] Type location Ethiopia, CASENT0904127

*Monomorium areniphilum Santschi, 1911[START_REF] Santschi | Fourmis nouvelles éthiopiennes[END_REF] Type location Tunisia, CASENT0249829 *Monomorium bicolor Emery, 1877[START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF] Type location Ethiopia, CASENT0904601 *Monomorium dakarense [START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF][START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF] Type location Senegal, CASENT0913570 *Monomorium osiridis Santschi, 1915 Type location Kenya, CASENT0913828 Monomorium pharaonis (Linnaeus, 1758) [START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF] Type location Egypt; no type images, well known tramp species Monomorium rosae Santschi, 1920[START_REF] Bolton | A review of the Solenopsis genus-group and revision of Afrotropical Monomorium Mayr (Hymenoptera: Formicidae). Bulletin of the British Museum (Natural History)[END_REF] [START_REF] Bolton | A review of the Solenopsis genus-group and revision of Afrotropical Monomorium Mayr (Hymenoptera: Formicidae). Bulletin of the British Museum (Natural History)[END_REF] Type location Ghana, CASENT0902248 *Monomorium sp Undescribed new species Myrmicaria opaciventris Emery, 1893[START_REF] Forel | Fourmis du Musée de Bruxelles. Fourmis de Benguela récoltées par M. CreightonWellman, et fourmis du Congo récoltées par MM. Luja, Kohl et Laurent[END_REF] Type location Angola, CASENT0904466 *Pheidole aeberlii Forel, 1894[START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF] Type location Senegal, CASENT0907803 *Pheidole andrieui Santschi, 1930 Type location Mali, CASENT0913264 *Pheidole bequaerti Forel, 1913 Type location Democratic Republic of Congo, CASENT0907845 *Pheidole megacephala (Fabricius, 1793) [START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF] Type location unknown, "Isle de France" (a suburb of Paris); no type images; well known tramp species *Pheidole mentita [START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF] Type location Guinea, CASENT0913348 *Pheidole rugaticeps Emery, 1877[START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF] Type location Eritrea, CASENT0904214 *Pheidole termitophila Forel, 1904[START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF] Type location South Sudan, CASENT0907853 *Pheidole welgelegenensis Forel, 1913 New status here; raised from race of P. sculpturata Type location Democratic Republic of Congo, CASENT0249075 *Tetramorium angulinode [START_REF] Santschi | Nouveaux dorylines africains[END_REF] Type location Congo, (Antweb) ZFMKHYM20096255 *Tetramorium muscorum Arnold, 1926 Type location Mozambique, CASENT0901145 *Tetramorium rothschildi Forel, 1907 Type location Ethiopia, CASENT0915429 *Tetramorium sericeiventre Emery, 1877[START_REF] Bolton | The ant tribe Tetramoriini (Hymenoptera: Formicidae). The genus Tetramorium Mayr in the Ethiopian zoogeographical region[END_REF] Type location Eritrea, CASENT0102073 *Tetramorium simillimum (F Smith, 1851) Type (Forel, 1902) Type location India, CASENT0249904 *Trichomyrmex oscaris (Forel, 1894[START_REF] Forel | Note sur quelques fourmis d'Afrique[END_REF] Type location Ethiopia, CASENT0908712 PONERINAE *Anochetus bequaerti Forel, 1913 Type location Democratic Republic of Congo, (Antweb) RMCAENT000017738 *Anochetus rothschildi Forel, 1907 Type location Somalia, CASENT0907412 *Anochetus sedilloti Emery, 1884[START_REF] Santschi | Descriptions de nouveaux formicidés éthiopiens et notes diverses. 1[END_REF] Type location Tunisia, CASENT0900511 *Brachyponera sennaarensis [START_REF] Mayr | Myrmecologische Studien[END_REF][START_REF] Santschi | Quelques nouveaux formicidés africains[END_REF] Type location Sudan, CASENT0902474 Leptogenys longiceps [START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF][START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF] Type location Senegal, no type images Megaponer analis [START_REF] Latreille | Histoire Naturelle des Fourmis, et recueil de mémoires et d'observations sur les abeilles, les araignées, les faucheurs, et autres insectes[END_REF][START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF]; [START_REF] Bogart | Insectivory of Savanna Chimpanzees (Pan troglodytes verus) at Fongoli, Senegal[END_REF] Type location Ghana, no type images Mesoponera caffraria (F Smith, 1858b) [START_REF] Agbogba | Observations on the feeding-preparation signals of larvae in the ponerine ant Pachycondyla caffraria (Smith)[END_REF][START_REF] Agbogba | Settlement in the prey termite nest by the ponerine ant Pachycondyla caffraria (Smith), and tandem running signal analysis for the following ant[END_REF]; [START_REF] Agbogba | Division of labour between foraging workers of the ponerine ant Pachycondyla caffraria (Smith) (Hymenoptera: Formicidae)[END_REF] Type location South Africa, queen CASENT0902479

Mesoponera senegalensis [START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF][START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF] Type location Senegal, CASENT0915273 *Paltothyreus tarsatus (Fabricius, 1798) [START_REF] Santschi | Formicidés de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri[END_REF] Type location Senegal, no type images PSEUDOMYRMECINAE *Tetraponera claveaui [START_REF] Santschi | Glanure de fourmis africaines[END_REF][START_REF] Santschi | Glanure de fourmis africaines[END_REF] Type location Senegal, CASENT0915524