Bernard Molin
email: bernard.molin@ec-marseille.fr

Fabien Remy
email: fabien.remy@ec-marseille.fr

Alain Ledoux
email: alain.ledoux@principia.fr

Nicolas Ruiz
email: nicolas.ruiz@principia.fr

EFFECT OF ROOF IMPACTS ON COUPLING BETWEEN WAVE RESPONSE AND SLOSHING IN TANKS OF LNG-CARRIERS

An experimental campaign is reported on the wave response of a rectangular barge supporting two rectangular tanks partly filled with water. Flat and chamfered tank roofs are successively tested, at varying heights above the free surfaces inside the tanks.

The tests are carried out in irregular wave systems coming from abeam. The measured barge roll and sloshing motions in the tanks are compared with numerical results from a linearized potential flow model. Good agreement is reported in mild seastates. Nonlinear effects, associated with large amplitude sloshing motion and/or roof impacts, are investigated.

INTRODUCTION

In [START_REF] Molin | LNG-FPSO's: frequency domain, coupled analysis of support and liquid cargo motions[END_REF] a theoretical model was proposed to couple liquid motion in tanks and sea-keeping of the floating support. This model relies on linearized potential flow theory and decomposes the sloshing motion in tanks over a finite number of modes, with the modal amplitudes obeying simple spring-mass equations. Numerical implementation was first performed in 2D configurations, then a specific module was developed within the DIODORE TM software of Principia. Dedicated experiments were performed in the wavetank BGO-First with a rectangular barge equipped with two rectangular tanks, submitted to irregular beam seas (see figure 1). Different water levels in the tanks were achieved, and difference surface conditions (smooth or rough). * Address all correspondence to this author.

Good agreement was obtained between experimental and numerical response amplitude operators (RAOs), both for the roll motion of the barge and for the liquid motion in the tanks, except at very low filling heights. In these experiments, as can be seen in figure 1, the tanks had no roofs.

Recently a new series of experiments was carried out, with the same model, and with the tanks fitted with roofs. The water level was kept the same throughout the tests, while the roofs were set at different heights above the free surfaces. The roofs were successively flat and chamfered.

In this paper we first recall the theoretical model presented in [START_REF] Molin | LNG-FPSO's: frequency domain, coupled analysis of support and liquid cargo motions[END_REF]. Then we describe the new experiments performed and we present a detailed comparison between the measurements and the computational results, obtained with a 2D semi-analytical model and with the DIODORE TM software.

THEORY Natural sloshing modes

The first step is to determine the natural sloshing modes for each tank, at its filling height. This means obtaining the nontrivial solutions of the following boundary value problem: ∆ϕ = 0 within the fluid volume (1) ∇ϕ • n = 0 on the walls S C

(2)

g ϕ z -ω 2 ϕ = 0 at the free surface S F (3)
where Φ(x, y, z,t) = ϕ(x, y, z) sin(ωt + θ)

For a two-dimensional rectangular tank, of length b and height of liquid h, the eigen-modes are given by

Φ n = - A n0 g ω n cosh λ n (z + h) cosh λ n h cos λ n y sin(ω n t + θ n ) (4)
where the natural frequencies ω n are

ω 2 n = g λ n tanh λ n h with λ n = n π b (5)
and the free surface elevation is

η n (y,t) = A n0 cos λ n y cos(ω n t + θ n ) (6)
(in a reference system Oxz such that O is located at the intersection of the free surface and one of the vertical walls). For a tank of general shape the eigen-modes can be obtained with a numerical software.

It is easy to show that the potentials ϕ n (x, y, 0) form an orthogonal and complete basis at the free surface.

As a result the free surface elevation can be expanded as

η(x, y,t) = ∑ n A n (t) ζ n (x, y) (7)
where

ζ n (x, y) = ω n g ϕ n (x, y, 0) (8)
(the elementary potentials ϕ n being normalized so that, for instance, max ζ n (x, y) = 1).

The velocity potential within the tank is then given by

Φ(x, y, z,t) = -∑ n t 0 A n (τ) dτ ω n ϕ n (x, y, z) (9)
This is correct under the condition that the tank be motionless, since Φ satisfies the homogeneous Neumann condition at the walls.

Elementary forced motion problems

Now we consider the tank undergoing forced motion along one of its 6 degrees of freedom. The elementary problems to be solved are

∆ϕ j = 0 fluid domain (10) ∇ϕ j • n = N j at S C (11) g ϕ jz -ω 2 ϕ j = 0 at S F (z = 0) (12)
the frequency ω being given. N j stands for one component of the generalized normal vector.

The potential ϕ j is looked for as:

ϕ j = φ j + ψ j (13)
where φ j is the infinite frequency "radiation" potential, which satisfies

∆ φ j = 0 fluid domain (14) ∇ φ j • n = N j at S C (15)
φ j = 0 at S F (z = 0) (16)
It ensues that the additional potential ψ j satisfies

∆ψ j = 0 fluid domain (17) ∇ψ j • n = 0 at S C (18) g ψ jz -ω 2 ψ j = -g φ jz at S F (z = 0) ( 19
)
The solution is straight-forward when one has projected φ jz (x, y, 0) on the basis ϕ n (x, y, 0):

φ jz (x, y, 0) = ∑ n S F φ jz ϕ n dS S F ϕ 2 n dS ϕ n (x, y, 0) = ∑ n γ jn ϕ n (x, y, 0). ( 20
)
One obtains

ψ j (x, y, z) = -g ∑ n γ jn ω 2 n -ω 2 ϕ n (x, y, z) (21)
The sum φ j + ψ j is the velocity potential resulting from a unit velocity amplitude along degree of freedom j. When one relates the amplitude A n of the sloshing motion n to the motion amplitude X j , one obtains the RAO

A n /X j = - ω 2 g γ jn ω n (ω 2 n -ω 2 ) = - ω 2 ω 2 n -ω 2 D n j (22)
It is equivalent to write that A n (t) obeys the pendulum equation

Än + ω 2 n A n = D n j Ẍj (23)
which remains valid when X j (t) is not harmonic since the D n j coefficients do not involve the frequency ω. They are defined by

D n j = g ω n S F φ jz ϕ n dS S F ϕ 2 n dS (24)
Making use of the integral identities

S F φ jz ϕ n dS = S F φ jz ϕ n -φ j ϕ nz dS = - S C ∇ φ j • n ϕ n -∇ϕ n • n φ j dS = - S C N j ϕ n dS (25)
we obtain the alternative expression

D n j = - g ω n S C ϕ n N j dS S F ϕ 2 n dS (26)
Hydrodynamic forces at the walls From the above analysis the velocity potential within the tank is given by

Φ(x, y, z,t) = -∑ n t 0 A n (τ) dτ ω n ϕ n (x, y, z) + 6 ∑ j=1 Ẋj (t) φ j (27)
The hydrodynamic pressure being

p = -ρ Φ t = ρ ∑ n A n (t) ω n ϕ n -ρ 6 ∑ j=1 Ẍj (t) φ j (28)
the hydrodynamic loads are given by

F = S C p n dS (29) C = S C p r ∧ n dS (30)
i.e., introducing the generalized force tensor F = ( F, C):

F = ∑ n A n (t) f n -M a (∞) ¨ X ( 31
)
where M a (∞) is the infinite frequency added mass matrix and

f n j = ρ ω n S C ϕ n N j dS (32)
It may be noticed that the f n j and D n j coefficients are obtained through the same integral over S C and that they are simply related:

D n j = - g ρ f n j ω 2 n S F ϕ 2 n dS (33)
Furthermore, the following identity, helpful for numerical checks, holds

M ai j (∞) -M ai j (0) = ∑ n f ni D n j ω 2 n = -ρ g ∑ n S C ϕ n N i dS S C ϕ n N j dS ω 2 n S F ϕ 2 n dS (34)

Coupled motion equations

All there remains to do is to couple the motion equations of the barge and the pendulum equations for the sloshing motions in each tank. In the latter linear and quadratic dissipation terms are introduced, giving

Äin + B 1in Ȧin + B 2in Ȧin | Ȧin | + ω 2 in A in = 6 ∑ j=1 D in j Ẍi j (35)
Here the suffix i stands for tank number i and X i j is the jcomponent of the barge motion, at tank i.

The damping terms can be related to frictional energy losses at the walls (see [START_REF] Molin | LNG-FPSO's: frequency domain, coupled analysis of support and liquid cargo motions[END_REF]), or, heuristically, to other sources of internal energy dissipation like wave breaking. Energy dissipation in the coupled mechanical system is also ensured by outer radiation damping and by the viscous damping in roll, which is found to play the dominant role. In the numerical model, the viscous damping moment in roll is expressed by

C v4 = - 1 2 ρC d B 4 L | α| α (36)
where C d is a non-dimensional coefficient, B is the beam of the barge, L its length and α the roll velocity.

In the resolution, the so-called "stochastic linearization" is applied, meaning that the damping moment is written as

C v4 = - 2 π ρC d B 4 L σ α α (37)
where σ α is the standard deviation of the roll velocity. This procedure ensures identical energy dissipations for gaussian processes.

It ensues that the combined equations of motion need to be solved through iterations, for a given sea-state specified by its energy spectrum. At each iteration the standard deviation σ α of the roll velocity is re-actualized. Convergence is usually reached within a few iterations. The same procedure is applied to the quadratic damping terms in equations (35).

EXPERIMENTAL CAMPAIGN

The experiments were carried out in the wave tank BGO-First, at la Seyne sur mer. This facility is 16 m wide, for a total length around 40 m. Thanks to a false bottom the water-depth can be varied from near 0 up to 5 m. During the experiments, it was set at 3 m.

The same barge model as in the previous campaign was used. It is 3 m long and 1 m wide, with a depth of 26.7 cm. The draft during the tests was 11 cm.

Two identical rectangular glass tanks were used, 80 cm long and 25 cm wide, with a height of 60 cm. These values refer to the internal dimensions. The two tanks were installed on the deck, with their lengths in the transverse direction of the barge model. They were filled with water at a depth of 29 cm, meaning 116 kg of water, while the mass of the model with the empty tanks (including instrumentation) was 176 kg. This is a configuration that was considered in the previous campaign; the only difference is that, due to the weight of tank roofs, force sensors and aerial camera, in this new campaign the total weight is a little bit larger (by 5 kg) and the center of gravity somewhat higher (29 cm above keel line vs. 24 cm). The roll radius of inertia of the barge with the tanks empty was around 42 cm.

The roofs in the tanks could be adjusted in position. They were located successively at 29 cm (no free surface), 35 cm, 40 cm and 45 cm above the tank floors, meaning airgaps of 0 cm, 6 cm, 11 cm and 16 cm. Then the roofs were fitted with chamfered corners, 18 cm × 18 cm. Successive roof positions at 35 cm, 40 cm, 45 cm and 50 cm above tank floors were then achieved, meaning airgaps of 6 cm, 11 cm, 16 cm and 21 cm. At 16 cm, the bottom ends of the chamfers were slightly below the still water level (by 2 cm), the length of which was shortened by 4 cm. At 11 cm the still water length was reduced by 14 cm, down to 66 cm. At 6 cm it was reduced by 24 cm, down to 56 cm. These are the three cases when the natural sloshing modes in the tank must be determined numerically.

The barge was moored by an horizontal cables + springs system. The resulting natural period in sway was 10.8 s.

Instrumentation consisted in the optical tracking RODYM system, giving the 6 dof motion with a very high accuracy. The free surface in one of the tanks was tracked optically with an onboard video camera. Image processing yielded the experimental modal amplitudes. Another onboard camera was set above one of the tanks, shooting down vertically so as to visualize the wetted area on the underside of the transparent roof. The vertical loads on the other roof were measured through a combination of 3 force sensors.

The tests were run in irregular waves coming from abeam. The seastates were calibrated without the barge model. The spectra were of JONSWAP type, with γ = 2, and peak periods T P of 1.6 s and 2 s. At 1.6 s, the specified H S values were 6 cm, 9 cm and 12 cm (seastates Irr1, Irr2, Irr3). At 2 s they were 8 cm, 12 cm and 16 cm (Irr4, Irr5, Irr6). These are somewhat stronger seastates than in the previous campaign (see [START_REF] Molin | LNG-FPSO's: frequency domain, coupled analysis of support and liquid cargo motions[END_REF]); at a scale of 1:50, the full-scale significant waveheights would be 3 m, 4.5 m, 6 m at a peak period of 11.3 s, and 4 m, 6 m, 8 m at a peak period of 14.1 s. The test duration was 600 s and the sampling rate was 100 Hz.

In this paper we focus on the first three seastates, for which the peak frequency is closer to the natural frequencies of the coupled roll and sloshing motions.

COMPARISONS BETWEEN EXPERIMENTAL AND NU-MERICAL RESULTS

Closed tanks

We start with the case when the roofs are lowered down to the free surfaces, inhibiting their motions. Still the water inside the tanks does not move as a solid body when the barge rolls. The roll inertia is lower than if the water were frozen; in our case, when related to the center-point of the tank, it is 65 % of the solid value.

Figures 2 and3 show the experimental and numerical roll RAOs for the seastates Irr1 and Irr3. The computed ones are obtained with the 2D model, with viscous roll coefficients C d of 0.12, 0.15 and 0.20. For the milder sea-state a good agreement is obtained with C d = 0.20, while in the stronger one C d = 0.15 gives the best fit. This suggests that the viscous damping moment in roll is not strictly quadratic with the roll velocity.

Flat roofs

In this section we consider the cases with the roofs flat (no chamfers). Three distances from the roofs to the mean free surface were considered in the tests, that is 6, 11 and 16 cm (configurations P35, P40 and P45). In the numerical model, which is linear (except for the roll viscous damping and the quadratic damping term in the tanks), there are no roofs. The question that we address here is to what extent the results given by our numerical model deviate from measurements as the roof clearance decreases. Rognebakke & Faltinsen [START_REF] Rognebakke | Damping of sloshing due to tank roof impact[END_REF] have proposed that roof impacts induce some damping of the sloshing motion; so it could be a matter of properly tuning the damping coefficients in the pendulum equations of the sloshing modes (35).

Roofs at 16 cm above water level

Here we consider the roofs in their highest position (P45), 16 cm above the still water level.

Seastate Irr1

Figure 4 shows numerical and experimental RAOs of the barge roll motion, for the mildest seastate Irr1 (H S = 6 cm, T P = 1.6 s). In this seastate no roof impact was observed. Numerical RAOs have been obtained with the 2D model, with different amounts of viscous roll damping (Cd = 0.15 and Cd = 0.20), while the linear damping in the tanks is set at 0 or 2 % of critical damping. The best fit is obtained with C d = 0.20 (as in the previous case) and no damping in the tank (in agreement with the results from the previous campaign -see [START_REF] Molin | LNG-FPSO's: frequency domain, coupled analysis of support and liquid cargo motions[END_REF]).

The video recording of the onboard camera (see figure 9) was processed in order to derive experimental RAOs of the am- plitudes of the sloshing modes. Figure 5 shows, for the same seastate Irr1, the experimental RAO of the first sloshing mode, compared with the computed ones. (This refers to the sloshing motion in the moving coordinate system, i.e. the modal amplitude A 1 is modified to account for the roll motion of the barge).

As with the roll motion the best fit is obtained with no damping in the tanks.

Next figure 6 shows the RAO of the amplitude of the second odd mode (n = 3, the first even mode n = 2 being nil according to our linear model). Experimental and numerical values are only about 10 % of the first mode's. It can be observed that the experimental RAOs somewhat exceed the numerical ones, whatever the amount of damping. This discrepancy is presumably associated with free surface nonlinearities.

Seastate Irr3

Figure 7 shows the experimental roll RAO in seastate Irr3, and the computed ones with 0 and 5 % internal damping in the tanks. With 5 % damping the height of the second peak agrees well with the experimental one but the location is not correct: as compared to seastate Irr1 the experimental peak has shifted toward lower frequencies. This can also be observed in figure 8 which shows the exper- imental RAOs of the first sloshing mode for the three seastates Irr1, Irr2 and Irr3. Noticeable are the shifts of the peaks toward lower frequencies, while the curves get flatter, as the severity of the seastates increases. The frequency shift may be attributed to nonlinear free surface effects: third-order theory predicts such frequency shifts (e.g. see [START_REF] Moiseev | On the theory of nonlinear vibrations of a liquid of finite volume[END_REF]). In our numerical model this presumably could be accounted for by adding up nonlinear (cubic) restoring terms in the pendulum equations (35), rendering them Duffing-like. Other roof elevations Figure 9 shows a view of the tank, from the onboard video camera, with the flat roof 11 cm above the mean free surface. In figure 10 we show the experimental RAOs of the roll motion in seastate Irr3 for the three positions of the roofs P45 (16 cm above free surface), P40 (11 cm above) and P35 (6 cm). The number of recorded roof impacts was, respectively, 27, 89 and 149 (over about 375 wave cycles). In the figure we also show, for reference, the experimental RAO in seastate Irr1 at the highest roof elevation (see figure 4). Surprisingly the first three curves are nearly coincident, despite the large differences in roof impacts.

This suggests that the decrease of the second peak of the roll RAO, when the seastate becomes stronger, is not only due to increasing energy dissipation but also to some other effects, probably associated with the nonlinearities in the free surface equations. This point deserves further investigation.

Chamfered roofs

Except for the configuration P50, the chamfers are penetrating the free surface. This means that the natural sloshing modes in the tanks cannot be determined analytically any more, so we use DIODORE TM , both to compute the hydrodynamic characteristics of the barge (diffraction loads, added masses and dampings) and the sloshing modes and infinite frequency added masses of the tanks.

Figure 11 shows the mesh of the tank in the P35 configuration. Figure 12 shows a view of the chamfered tank from the onboard video camera. P40 configuration Figures 15 and 16 refer to the P40 case, meaning the bottom ends of the chamfers are 7 cm below the free surface, the length of which is reduced from 80 to 66 cm. Figure 15 shows the experimental and numerical roll RAOs, in the milder seastate Irr1. As a result of the reduced free surface length, the second peak has been shifted toward higher frequencies and reduced in size. Figure 16 refers to the seastate Irr3: the second peak, associated with the sloshing motion, has almost disappeared from the experimental RAO. In the calculations an internal damping of 5 % of critical has been added up (no additional damping was introduced in seastate Irr1).

P35 configuration

In the P35 configuration the chamfers are more deeply immersed and the free surface length is reduced to 56 cm. Figures 17 and 18 show the experimental and numerical roll RAOs in seastates Irr1 and Irr3, also with (respectively) 0 and 5 % internal damping. The natural frequency of the first sloshing mode has shifted even higher and its effect on the barge roll motion has become hardly noticeable.

CONCLUSION

In mild seastates, good agreement has been reported between calculated and measured roll RAOs, whatever the shapes (flat or chamfered) and positions of the roofs. The energy dissipation that takes place in the tanks in insignificant.

As the seastate becomes more severe, nonlinear effects come into play: the second peak of the roll RAO decreases and flattens, while it shifts toward lower frequencies. Numerically the decrease and flattening can be rendered by introducing some energy dissipation in the tanks. Surprisingly hardly no difference can be observed in the experimental roll RAOs when the airgap between the flat roofs and the free surface varies, even though the number and intensity of roof impacts are very different. This suggests that the decrease of the second peak may not be so much due to internal dissipation than to free surface nonlinearities. This point deserves further investigations.

With chamfered corners, decreasing the airgap also means decreasing the free surface area and increasing the natural frequency of the sloshing motion. As a result the coupling effects between sloshing motion and roll response weaken.

These conclusions refer to the tested cases. They do not pretend to have any degree of generality when the geometries of the tanks and floating support, or filling ratios, vary.

Figure 1 .

 1 Figure 1. BARGE MODEL IN THE BASIN (FROM [1]).

Figure 2 .

 2 Figure 2. CLOSED TANKS. EXPERIMENTAL AND NUMERICAL ROLL RAOS. SEASTATE IRR1.

Figure 3 .

 3 Figure 3. CLOSED TANKS. EXPERIMENTAL AND NUMERICAL ROLL RAOS. SEASTATE IRR3.

Figure 4 .Figure 5 .

 45 Figure 4. ROLL RAO. FLAT ROOF 16 CM ABOVE STILL WATER LEVEL. SEASTATE IRR1.

Figure 6 .

 6 Figure 6. RAO OF THE SECOND ODD MODE. FLAT ROOF 16 CM ABOVE STILL WATER LEVEL. SEASTATE IRR1.

Figure 7 .

 7 Figure 7. ROLL RAO. FLAT ROOF 16 CM ABOVE STILL WATER LEVEL. SEASTATE IRR3.

Figure 8 .

 8 Figure 8. RAO OF THE FIRST SLOSHING MODE. FLAT ROOF 16 CM ABOVE STILL WATER LEVEL. SEASTATES IRR1, IRR2, IRR3.

Figure 9 .

 9 Figure 9. FLAT ROOF IN P40 CONFIGURATION. VIEW FROM THE ONBOARD VIDEO CAMERA (NUMBERS ARE PIXELS).

Figure 10 .

 10 Figure 10. ROLL RAO FOR DIFFERENT ROOF ELEVATIONS.

Figure 11 .

 11 Figure 11. CHAMFERS AT 12 CM IMMERSION. MESH OF THE TANK.

Figure 12 .

 12 Figure 12. CHAMFERS IN P45 CONFIGURATION. VIEW FROM THE ONBOARD VIDEO CAMERA.

Figure 13 .Figure 14 .

 1314 Figure 13. CONFIGURATION P45. SEASTATE IRR1. MEASURED AND CALCULATED ROLL RAOS.

Figure 14

 14 Figure14refers to the seastate Irr3 and shows the experimental and numerical roll RAOs, obtained with 0 and 5 % internal damping. The second peak of the experimental RAO appears to be somewhat blurred and shifted toward lower frequencies. Again, like in the flat roof case, with 5 % internal damping, the peak level (if not the shape) is well rendered.

Figure 15 .

 15 Figure 15. CHAMFERS 7 CM IN WATER. SEASTATE IRR1. MEA-SURED AND CALCULATED ROLL RAOS.

Figure 16 .

 16 Figure 16. CHAMFERS 7 CM IN WATER. SEASTATE IRR3. MEA-SURED AND CALCULATED ROLL RAOS.

Figure 17 .

 17 Figure 17. CHAMFERS AT 12 CM IMMERSION. SEASTATE IRR1. MEASURED AND CALCULATED ROLL RAOS.

Figure 18 .

 18 Figure 18. CHAMFERS AT 12 CM IMMERSION. SEASTATE IRR3. MEASURED AND CALCULATED ROLL RAOSs.


Philene Corinne Aude

Um Nyobe

Sevilor Kekeunou
email: skekeunou@gmail.com

Libin Ma
email: libinma@snnu.edu.cn

Tony Robillard
email: tony.robillard@mnhn.fr

Alain Simeu-Noutchom

Charles Felix

Bilong Bilong
email: bilong_bilong@yahoo.com

Charles Felix Bilong Bilong

Description and bioecology of two new species of the genus Cryncus (Orthoptera, Gryllidae, Gryllinae) from Cameroon with a key and distribution map of all African species

Keywords: Cryncus, Afrotropical region, Taxonomy, Distribution, Zamakoe Cryncus, Afrotropical region, Taxonomy, Distribution, Zamakoe

niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Biological diversity, a driving functioning of the ecosystems, remains badly known still nowadays, especially for groups of insects which are not emblematic. Crickets (Grylloidea), which count approximately 4,500 species, live for the majority in tropical area and are diversified particularly in wet tropical zone [START_REF] Chopard | Orthoptéres et Aptérygotes de France[END_REF]. The composition of their settlements is strongly influenced by the environments (savannah, field, fallow, forest), their rhythms of life and their ecological preferences (Chiffaud-Mestre & Gillon 1984). Given the accelerated rhythm of conversion of forests into grassy vegetations in the world, the study of biological diversity of crickets is essential in order to have a knowledge pushed on these latter.

The genus Cryncus [START_REF] Gorochov | New genera and species of crickets of the subfamily Gryllinae (Orthoptera,Gryllidae) from Africa[END_REF] is currently known only from the African continent. [START_REF] Gorochov | New genera and species of crickets of the subfamily Gryllinae (Orthoptera,Gryllidae) from Africa[END_REF][START_REF] Gorochov | Ensifera from tropics and subtropics (Russian)[END_REF] described seven species of Cryncus and five others transferred from Gryllopsis [START_REF] Chopard | Catalogues raisonnes de la faune entomologique de Congo Belge. Orthoptères Gryllides[END_REF][START_REF] Chopard | Contributions à 1'étude de la Faune du Mozambique. Voyage de M. P. Lesne[END_REF][START_REF] Chopard | Parc National Albert[END_REF][START_REF] Chopard | Contribution à la faune du Congo (Brazzaville). Mission A. Villiers et A. Descarpentries. L. Orthoptères, Grylloidea[END_REF], all being found in West, East and North Africa. [START_REF] Otte | African crickets (Gryllidae: Gryllinae).7. The genus Cryncus Gorochov[END_REF] also transferred one additional species from Gryllopsis and described nine others from South and East Africa. Nowadays, the genus Cryncus encompasses twenty-three species with records in Egypt, Zambia, Burkina, Democratic Republic of Congo, Sierra Leone, Ghana, Djibouti, Tanzania, Kenya and Ethiopia (Orthoptera Species File online). Prior to the current work, Cryncus has been only reported in one country of Central Africa (Democratic Republic of Congo). We report its presence for the first time in Cameroon. The morphology of East African Cryncus spp. is very similar; they can only be reliably distinguished by the male songs [START_REF] Otte | African crickets (Gryllidae: Gryllinae).7. The genus Cryncus Gorochov[END_REF]. According to [START_REF] Otte | African crickets (Gryllidae: Gryllinae).7. The genus Cryncus Gorochov[END_REF], all of them might have been treated as a single species if their songs had not been known. In addition, Cryncus pugu [START_REF] Otte | African crickets (Gryllidae: Gryllinae).7. The genus Cryncus Gorochov[END_REF] is only recognizable by its song until its formal morphological description. However, [START_REF] Desutter-Grandcolas | Reflections on the growing use of sounds in systematics and synecology: why an acoustic signal cannot become an onomatophore[END_REF] have shown limits in the use of acoustic data to formally describe new taxa by the sole acoustic productions of unseen specimens, forcing a 'sound-based taxonomy' on traditional taxonomy, hence the interest in taxonomy of associating morphological description and bioacoustics. Besides, morphological and bioecological data remain essential in the taxonomy of ensiferans (Simeu-Noutchom et al. 2020). The aim of this work is to update the taxonomic, bioecological and biogeographical knowledge of Cryncus through the description of two new species from Cameroon.

Materials and Methods

Sampling localities. Specimens studied were sampled in habitats with different levels of anthropisation (Table 1) defined according to the benchmark by [START_REF] Gockowski | Quelques données de l'enquête agricole dans les villages de recherche[END_REF]. [START_REF] Gockowski | Quelques données de l'enquête agricole dans les villages de recherche[END_REF] Sampling was carried out in Zamakoe, Ongot and Engout'Adjap (Fig. 1) in two types of vegetation: closed (forests) and open environments (fallows). The southern Cameroonian forest is dominated by Sterculiaceae and Ulmacae; its undergrowth is made up of herbaceous plants such as Maranthaceae and Acanthaceae [START_REF] Westphal | L'agriculture autochtone au Cameoun Miscellaneous papers 20: Landbouwhogescool[END_REF]. In this area, the natural vegetation is regularly degraded by the economic exploitation of wood and the practice of slashand-burn agriculture [START_REF] Santoir | Gryllotalpa weisei Simeu-Noutchom & Kekeunou sp. nov. and the first record of Gryllotalpa microptera (Chopard 1939) (Orthoptera, Gryllotalpidae) from Cameroon with redescription of the species[END_REF]. The resulting bushy vegetation after degradation is less diversifed and dominated by Chromolaena odorata, Ageratum conizoides, Synedrella nodiflora, and Imperata cylindrica. Plantain, cassava, yam, maize, and groundnut are the main food crops, while industrial ones include cocoa, coffee, sweet banana, and palm oil [START_REF] Westphal | L'agriculture autochtone au Cameoun Miscellaneous papers 20: Landbouwhogescool[END_REF][START_REF] Oumarou Ngoute | Effect of anthropogenic pressure on grasshopper (Orthoptera: Acridomorpha) species diversity in three forests in southern Cameroon[END_REF]. The southern Cameroon plateau has an equatorial climate type with four seasons, including a long dry season (LDS) from mid-November to mid-March, a short rainy season (SRS) from mid-March to June, a short dry season (SDS) from July to mid-September, and a long rainy season (LRS) from mid-September to mid-November [START_REF] Suchel | Les régions climatiques du Cameroun. Les climats du Cameroun[END_REF]. Precipitations range from 1500-2000 mm per year [START_REF] Amou'ou | Le Cameroun[END_REF][START_REF] Santoir | Gryllotalpa weisei Simeu-Noutchom & Kekeunou sp. nov. and the first record of Gryllotalpa microptera (Chopard 1939) (Orthoptera, Gryllotalpidae) from Cameroon with redescription of the species[END_REF]. The average annual rainfall is 1510 mm, 1643 mm and 1820 mm in Ongot, Zamakoe and Engout'Adjap respectively [START_REF] Kekeunou | Farmers' perception on the of variegated grasshopper (Zonocerus variegatus (L.)) in the agricultural production systems of the humid forest zone of Southern Cameroon[END_REF]. Average annual temperature is high (between 25 to 27 ° C) outside the forest canopy; under forest cover, temperature is low and humidity is constantly high [START_REF] Suchel | Les régions climatiques du Cameroun. Les climats du Cameroun[END_REF]). Soils are "Xanthic" or "Plinthic Ferralsols" (IUSS Working Group WRB 2015) and belong to the group of ferralitic soils strongly desaturated. There are clay soils from yellowish brown to bright brown, with pH generally acidic, very poorly drained hydromorphic soils in the shallows [START_REF] Robain | Presentation of the soils of South Cameroon. Organization and implementation at the scale of the landscape unit[END_REF]. Crickets were captured during the sampling day with the wipe net, the hand or with a mouth vacuum cleaner, then were kept in labeled boxes containing 70% ethanol for later identification.

Pitfall traps were made up of plastic cups (8 cm diameter and 12 cm deep) buried in the ground level and containing 5% formalin as preservative. Crickets captured by the pitfalls were collected a month later, transferred into labeled boxes, rinsed with water then stored in 70% ethanol in the same boxes.

Study material.

Observations of morphological characters were performed using a binocular magnifier Leica connected to an Amscope camera (Heerbrugg brand). The identifications were done by comparison with original species descriptions. The pictures of external morphology (Figs. 2 A-F and 3 A-F) were taken with specimens immersed in 70% ethanol, using a LCD Digital Microscope connected to a computer via USB cable. were made by CorelDRAW×8 software, while measurements were taken using a NEIKO electronic caliper. The maps of the study localities and species distribution were built with the software QGIS 2.2.0. Figure 4, representing the abundances of the species according to the type of vegetation, was realized using the software R 4.0.2 (R Core Team 2017).

Dissection of the phallic complex. Dissection of adult male's phallic complex was performed on specimens preserved in 70% ethanol, using dissection-tools and a binocular magnifier Leica.

The male genitalia were dissected by making a small slit between paraproct and subgenital plate. The isolated phallic complex was kept in a 5% KOH solution for 8 hours in an eppendoff tube in order to clear it. This organ was then immersed in distilled water for about 5 minutes, then in ethanoic acid for 30 minutes to neutralize the KOH solution, and finally in 1% fuchsine solution for 30 minutes to stain the sclerotized parts before observation. calculate the frequency of occurrence (FO) of each species (FO ≥ 50 %: constant species; 25 % ≤ FO < 50%: accessory species; FO < 25 %: accidental species). All tests values were considered significant for P <0.05. In tables 5 and 6, values preceding parentheses represent the number of sampling campaigns during which species was captured; those in parentheses represent frequency of occurrence obtained by the ratio between the number of descents where a species was present over the total number of descents in the field [START_REF] Dajoz | Précis d'écologie[END_REF].

Abbreviations used in morphological identification:

General morphology: FI, FII, FIII, fore, median, hind femora; FW, forewing; TI, TII, TIII, fore, median, hindtibia.

Terminology of forewing venation is according to Desutter-Grandcolas et al. (2017) as follows: cu.v., cubital vein;m.v., median vein;r.v., radial vein;sc.v., subcostal vein and its branches;o.v., oblique vein;d.v., diagonal vein;a.n., anal node;m., mirror;h., harp;c., cord;a.f., anal field; ap.f., apical field; l.f.,lateral field.

Abbreviations used for the measurements (mm):

Measurements were done in reference to [START_REF] Otte | African crickets (Gryllidae: Gryllinae).7. The genus Cryncus Gorochov[END_REF]: BL, body length; FL, hind femora length; TL, hindtibia length; FWL, forewing length; PL, pronotal length; ML, Mirror length; MW, Width of the mirror; OL, ovipositor length; CL, cercal length.

Abbreviations used in genitalia identification:

Terminology for genitalia is according to [START_REF] Desutter | Structure et évolution du complexe phallique des Gryllidea (Orthoptera) et classification des genres néotropicaux de Grylloidea. 1 re partie[END_REF] and [START_REF] Desutter-Grandcolas | Phylogeny and the evolution of acoustic communication in extant Ensifera (Insecta, Orthoptera)[END_REF] as follows: Ect.Ap., ectophallic apodeme; Ect.F., ectophallic fold; M.Lophi, median lophi; L.Lophi, lateral lophi; PsP, pseudepiphallic paramere; R, ramus. Etymology. Epithet camerounensis refers to the country where the type material was found.

Results

Systematic part

Diagnosis. Micropterous species with forewings reaching abdomen mid-length. Mirror of irregular shape, wider than long, without division and presenting a space between it and the apical field which is short (Fig. 2 C,G). Presence of an elongated oval tympanum on outer surface of anterior tibia; inner face without tympana. Posterior tibia with 5 dorsal spurs on each side (internal and external). Median lophi and ectophallic fold absent (Fig. 2 H,I).

Ectoparameres long, tapered and reaching apical end of epiphallic lobes without exceeding them (Fig. 2 H,I).

Description. (Fig. 2 A-I; Table 2)

Male. Head: presence of a pale brown interantennary stripe extending dorsally under each eye to terminal end of occiput, defining a nearly rounded black area containing two short pale brown lines on occiput. Short brown line posterior to eye (Fig. 2 A). Face with a black band above epistomal suture; cheeks black posterior to eye but pale brown below eye (Fig. 2 B). Pronotum: dorsum pale brown, with numerous small dark spots; lateral lobes with pale band in lower third (Fig. 2 A). Forewings: grayish brown on dorsal and lateral fields; veins dark brown; harp with 4 oblique veins; mirror of irregular shape, without division, and connected to first cord by two veinlets; mirror connected to the apical field only at its right end creating a space that separates them; presence of two cords strongly curved inwardly the elytra, and an outermost cord straight; apical field short, with irregularly shaped cells (Fig. 2 C,G). Hind wing vestigial under forewings. Abdomen: dorsum of abdomen dark brown, but with rows of light patches; venter pale. Cerci pale brown. Legs: front and middle legs: femora pale with dark spots on dorsum and sometimes with large dark patches on inner and outer faces; anterior tibia with two pale bands in basal half and one at distal end with large oval tympanum present on outer face; inner face without tympana; fore tibia with 6 and mid tibia with 2 apical spurs. Hind femora: pale in background, with dark pubescence; on lateral face dark pubescence usually arranged in oblique rows; femora darker around knees. Hind tibia: length 0.58 times length of femora; with 5 inner Figure 2. Morphology of Cryncus camerounensis sp. nov.: (A) male head and pronotum, (B) male lateral view of head and pronotum, (C) male forewing, (D) female head and pronotum, (E) female lateral view of head and pronotum, (F) female fore wing, (G) male forewing drawing, (H) male genitalia drawing in dorsal view, (I) male genitalia drawing in ventral view. Scale bars: A: 7 mm; B, C, E: 5 mm; D, 8 mm;F, 11 mm; G, 5 mm; H, I, 500 µm. and 5 outer subapical spurs. Cerci: pale brown; length 0.66 times as long as hind femora. Male genitalia: epiphallus bilobed; lobes pointed with U-shaped depression between them; ectoparameres long, tapered and reaching the apical end of the epiphallic lobes without exceeding them (Fig. 2 H,I). Female. Same characteristics as male except forewings, micropterous but truncated at their terminal end (Fig. 2 D,F). Forewings triangular, not overlapping at midline. Hindwings missing. Ovipositor: length 0.86 to 1.2 times the length of hind femora (Table 2).

Male holotype measurements: BL, 14.84 mm; PL, 2.46 mm; PW, 3.72 mm; FWL, 7.60 mm; ML, 2.92 mm; MW, 1.53 mm; CL, 6.68 mm; FL, 10.12 mm; FW, 3.32 mm; TL, 5.87 mm. File with 238 teeth. Diagnosis. Brachypterous species with forewings covering almost the entire abdomen with a long apical field and an oval mirror with a dividing vein (Fig. 3 C,G). Anterior tibia with two tympana: one small, round and internal, the other oval and elongated on external face. Hind tibia brownish with 5 dorsal spurs on the internal face and 6 dorsal spurs on the external face.

The first spur on the outer side very small. Median lophi tends to disappear and the ectophallic fold little individualized. Ectoparameres short, very large and do not reach the apical end of epiphallic lobes (Fig. 3 H,I).

Description. (Fig. 3 A-I; Table 3) Male. Head: Occiput with 3 brown dark bands, two short lateral ones posterior to eyes and a long median one extending up to interantennial space and presenting a light brown line at its middle (Fig. 3 A,D). Face speckled above epistomal suture and below level of antennae; cheeks black posterior to eye but pale brown below eye (Fig. 3 B). Pronotum: dorsum pale brown, with numerous small dark spots; lateral lobes with two pale spots (Fig. 3 A). Forewings: grayish brown on dorsal and lateral fields; veins dark brown; harp with 4 oblique veins; oval mirror with a dividing vein and connected to the first cord by two veinlets; presence of two cords weakly curved inwardly the elytra and one outermost cord straight; long apical field, with rectangular and triangular shaped cells (Fig. 3 C,G). Hindwings missing. Abdomen: dorsum of abdomen dark brown with rows of light patches; venter pale. Cerci pale brown. Legs: front and middle legs: femora pale with dark spots on dorsum and sometimes with large dark patches on inner and outer faces; tibia with two pale bands in basal half and one at distal end with large outer and a tiny inner tympanum; fore tibia with 6 and mid tibia with 2 apical spurs. Hind femora: pale in background with dark pubescence; on lateral face dark pubescence usually arranged in oblique rows; femora darker around knees. Hind tibia: length 0.69 times length of femora with 5 inner and 6 outer subapical spurs. Cerci: pale brown broken. Male genitalia: epiphallus bilobed; lobes pointed with U-shaped depression between them; ectoparameres short, very large not reaching the apical end of the epiphallic lobes (Fig. 3 H,I). Female. Same characteristics as male except forewings slightly exceeding half of the abdomen. There is a variation in coloration in females concerning the color of occiput and pronotum: some present Remarks. The comparison of the forewing characters in male Cryncus shows through the FWL / PL ratio that Cryncus desutterae sp. nov. has the longest forewings, followed by Cryncus grumeti [START_REF] Otte | African crickets (Gryllidae: Gryllinae).7. The genus Cryncus Gorochov[END_REF] with 4.77 and 3.18 respectively [START_REF] Otte | African crickets (Gryllidae: Gryllinae).7. The genus Cryncus Gorochov[END_REF][START_REF] Gorochov | New genera and species of crickets of the subfamily Gryllinae (Orthoptera,Gryllidae) from Africa[END_REF][START_REF] Gorochov | Ensifera from tropics and subtropics (Russian)[END_REF]. C. desutterae sp. nov. is similar to C. grumeti by the structure of the occiput, pronotum and forewings, but differs from it by the length of the ectoparameres which are long, broad and extend beyond the apical end of the epiphallic lobes in C. grumeti.

Revised Cryncus diagnosis. Vertex and occiput totally black or with 3 brown dark or black bands. Presence of one or two tympana on anterior tibia. Harp with 3 to 5 oblique veins. Apical field of elytra shorter or longer than the mirror. Female forewings short, triangular, not overlapping at the midline, or relatively long, slightly exceeding the abdominal half and partly overlapping in the middle. Hindwings absent or reduced to wing stumps. Hind tibia with a characteristic small pale patch at its distal end and having 5 dorsal spurs on the inner side and 5 or 6 dorsal spurs on the outer side. Epiphallus covered with bristles at its apical end. Median lophi tending to disappear in most species, ectophallic fold eventually present, very well or little individualized or totally absent.

Key for the species of Cryncus

This key is produced from morphological characters and excludes C. pugu which is only known by its song. . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .C. bifasciatus. 19b Bioecology. (Fig. 4; Tables 4 and5)

During 19 months of sampling in the three study localities, 19 specimens of Cryncus camerounensis were captured in forests and 2 others in fallows with a peaks of abundance in March and April 2015; as for Cryncus desutterae, only 6 individuals were captured in Zamakoe and Ongot exclusively in fallows (Fig. 4). Cryncus camerounensis was accessory (FO=26.32%) in forests and accidental in fallows (FO= 5.26%); while C. desutterae, although it was found exclusively in fallows, it remained accidental (FO= 15.78%), see table 4. Cryncus camerounensis was also captured with pitfalls (FO=26.32%) and accidentally with quadrats (FO= 5.26%); while C. desutterae was accidentally and only captured (FO= 15.78%) with pitfalls. In general, pitfalls allowed to sample the majority of specimens, see table 5.

Geographical distribution of Cryncus spp. and their type localities

All Cryncus spp. known to date are found mostly in the intertropical zone of the African continent (Fig. 5). . desutterae, C. illubabori, C. rybalovi, C. pulchellus, C. olsufievi, C. dmitrievi, C. apricus, C. notabilis, C. massarti. The shapes and sizes of these bands make it possible to distinguish the species [START_REF] Otte | African crickets (Gryllidae: Gryllinae).7. The genus Cryncus Gorochov[END_REF]. The particularity of C. camerounensis and C. desutterae is their pale brown pronotum spotted with a few small black dots. By this character, they are distinguishable from C. scenicus with an unspotted pronotum, C. superciliosus whose pronotum has numerous black dots and spots, and C. bifasciatus with two wide ivory bands on pronotum extending from antennae on cerci. According to [START_REF] Otte | African crickets (Gryllidae: Gryllinae).7. The genus Cryncus Gorochov[END_REF] the apical area is usually shorter than mirror, but in C. desutterae sp. nov. the apical area is longer than the mirror; so, depending on the species, the apical area can be shorter or longer than the mirror. Based on [START_REF] Otte | African crickets (Gryllidae: Gryllinae).7. The genus Cryncus Gorochov[END_REF] and [START_REF] Gorochov | New genera and species of crickets of the subfamily Gryllinae (Orthoptera,Gryllidae) from Africa[END_REF][START_REF] Gorochov | Ensifera from tropics and subtropics (Russian)[END_REF], we hypothesize that all species without a divided mirror have a short apical field while those with a divided mirror have a long apical field. We also noticed that C. massarti, the only known species without mirror, has a long apical field. All species of Cryncus have either four or five oblique veins in the harp (usually four as mentioned by [START_REF] Otte | African crickets (Gryllidae: Gryllinae).7. The genus Cryncus Gorochov[END_REF]). C. pulchellus is the only species which has only three oblique veins. Besides, C. camerounensis and C. desutterae have more teeth on the stridulatory file than the others species of the genus, with respectively 238 and 261 teeth. The ML / MW ratio shows that the new species have the longest mirrors with ratios of 1.71 and 1.58 respectively. Concerning females, those of C. desutterae also present longer forewings, with a ratio of 2.88. Female forewings are variable as mentioned by [START_REF] Otte | African crickets (Gryllidae: Gryllinae).7. The genus Cryncus Gorochov[END_REF], since two West African species have wings about twice as long as the pronotum and partly overlapping in the middle, while wings are generally triangular, do not overlap at the midline, and are 1.0 to 1.5 as long as the pronotum length in species from East Africa. The new species presented in this work, which belong to central Africa, we observed the presence of these two wing types. The OL / FL ratio for all species shows that the posterior femora are as long as the ovipositor; except for C. olsuflevi [START_REF] Gorochov | New genera and species of crickets of the subfamily Gryllinae (Orthoptera,Gryllidae) from Africa[END_REF]C. dmitrievi Gorochov, 1983 which have very short ovipositor [START_REF] Gorochov | New genera and species of crickets of the subfamily Gryllinae (Orthoptera,Gryllidae) from Africa[END_REF].

The concentration of Cryncus spp. in the intertropical zone could reflect a larger sampling effort in this zone. In other words, the lack of data concerning these species in some African countries could be due to the absence of sampling, or to a real absence of these species in these countries.

Cryncus spp. are entirely flightless; the east African species are commonly found in leaf litter in woodlands or in thick grasses at the edges of lowland forests [START_REF] Otte | African crickets (Gryllidae: Gryllinae).7. The genus Cryncus Gorochov[END_REF]. Since the frequency of occurrence of C. camerounensis sp. nov. is (26.32% < 50%) in forests and in fallows (<25%), its preferred habitat probably corresponds to the forest. C. desutterae sp. nov.

would prefer more open environments, since it was only captured in fallows with a frequency of occurrence <25%, which attests that it is accidental. A more increased sampling effort could provide a better idea of the habitat of these two species. Most individuals were captured by pitfalls and, this method seems more suitable to catch crickets. [START_REF] Chiffaud | Traits généraux et composition du peuplement des grillons de la savane de Lamto (Côte-d'ivoire) brûlée et non brûlée (orthoptera, gryllidae)[END_REF] reported that the quadrat sampling method leads to an underestimation of abundances in the case of small species, early stages of crickets, and individuals that take refuge in burrows.

However, since our study was carried out during the day, when crickets are generally inactive, it would be interesting to consider captures in the quadrats in the half-light, which corresponds to the moment when crickets are more active [START_REF] Chiffaud | Traits généraux et composition du peuplement des grillons de la savane de Lamto (Côte-d'ivoire) brûlée et non brûlée (orthoptera, gryllidae)[END_REF] to effectively compare this method to that of the pitfalls.

Figure 1 .

 1 Figure 1. Location of the sampling localities.

  Data analysis. Data were analyzed using Excel version 2010 and PAST version 3.2. These softwares allowed to: (1) calculate averages of measurements and standard errors; (2) verify the normality of distributions of quantitative variables by the Shapiro-Wilk test; (3) compare the means of measurements by the Student's test in case of normality and homoscedacity; (4) compare means of measurements using Mann-Withney test in absence of normality; (5)

  Cryncus olsufievi[START_REF] Gorochov | New genera and species of crickets of the subfamily Gryllinae (Orthoptera,Gryllidae) from Africa[END_REF] Cryncus camerounensis Um Nyobe,Kekeunou & Bilong Bilong sp. nov. Material examined. Holotype: male, CAMEROON, Center Region, Zamakoe (3°33'816"N, 11°31'913"E), secondary forest, 21/iii/2015; pitfall trap; P. Um Nyobe & team leg. (MNHN_EO_ENSIF1139). Paratypes:5 males, 14 females, CAMEROON, Center Region, Zamakoe (3°33'816"N, 11°31'913"E); principally in secondary forest, only two females in crops field (14/iii/2015, 16/ii/2015, 18/iv/2015, 21/iii/2015); pitfall trap mainly, quadrat trap occasionally (MNHN_EO_ENSIF10950-10968). 1 female, CAMEROON, Center Region, Ongot (3°85'786"N, 11°38'333"E), secondary forest, 08/ii/2015, pitfall trap (MNHN_EO_ENSIF10969); 1 male, CAMEROON, South Region, Engout'Adjap (2°42'N, 11°03'E), secondary forest, 09/06/2015, pitfall trap; P. Um Nyobe & team leg. (MNHN_EO_ENSIF10970).

  which is only connected to the apical field on the right lateral side, making a rather noticeable gap between the mirror and the apical field. C. camerounensis sp. nov. is similar to Cryncus duplicatus[START_REF] Otte | African crickets (Gryllidae: Gryllinae).7. The genus Cryncus Gorochov[END_REF] Cryncus impiger Otte, 1985 by the structure of the occiput and pronotum but, it differs from these species by the forewing and genitalic structures. C. duplicatus and C. impiger have 5 oblique veins and broad ectoparameres while C. camerounensis has 4 oblique veins with tapered ectoparameres. Cryncus desutterae Um Nyobe, Kekeunou & Ma sp. nov. Material examined. Holotype: male, CAMEROON, Center Region, Zamakoe (3°33'816"N, 11°31'913"E), in crops field, 20/vi/2015; pitfall trap; P. Um Nyobe & team leg. (MNHN_EO_ENSIF10971). Paratypes:1 male, 2 females, CAMEROON, Center Region, Zamakoe (3°33'816"N, 11°31'913"E); all in crops field, 20/vi/2015, pitfall trap exclusively (MNHN_EO_ENSIF10972-ENSIF10974). 1 male, 2 females, CAMEROON, Ongot (3°85'786"N, 11°38'333"E); all in crops field, (25/vii/2015, 20/xii/2014), pitfall trap exclusively; P. Um Nyobe & team leg. (MNHN_EO_ENSIF10975-ENSIF10977). Etymology. Cryncus desutterae Um Nyobe, Kekeunou & Ma sp. nov. is dedicated to Laure Desutter-Grandcolas for her background work on the taxonomy of crickets.

Figure 3 .

 3 Figure3. Morphology of Cryncus desutterae sp. nov.: (A) male head and pronotum, (B) male lateral view of head and pronotum, (C) male fore wing, (D) female head and pronotum, (E) female lateral view of head and pronotum, (F) female forewing, (G) male forewing drawing, (H) male genitalia drawing in dorsal view, (I) male genitalia drawing in ventral view. Scale bars: A, 9 mm; B, 8 mm; C, 5 mm; D, F: 7 mm; E, 6 mm; H, I, 500 µm..

  1a. Mirror absent. . .. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ……………….. C. massarti. 1b. Mirror present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2a. Fore wings with 3 oblique veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .……… C. pulchellus. 2b. Fore wings with more than 3 oblique veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . …3 3a. Short ovipositor less than 6mm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3b. Long ovipositor more than 6mm. . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4a. Very short ovipositor (1,3 mm). . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .C. dmitrievi.

  4b. Short ovipositor (4-4.5 mm)…... . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . C. olsufievi. 5a. Anterior tibia with a large oval tympanum on outer face, and a small round tympanum on inner face………. . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .6 5b. Anterior tibia with a large oval tympanum on outer face, and inner face without tympana.………………………………………………………………………………………..7 6a. Hind tibia with 5 inner and 6 outer subapical spurs. .. . . . . . . . . . . . . . . . . . . . . C. saussurei. 6b. Hind tibia with 5 inner and 5 outer subapical spurs….. . . . . . . . . C. camerounensis sp. nov. 7a. Pronotum pale brown and unspotted. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. scenicus. 7b. Pronotum pale brown spotted .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . ..8 8a. Presence of 4 dark prominent points along the posterior edge of the pronotum and lateral lobes completely black. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . C. rybalovi. 8b. Presence of small dark dots on pronotum and lateral lobes with pale band in lower third……. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 9a. Long ectoparameres extending beyond the apical end of the epiphallic lobes. . . . C. grumeti. 9b. Short ectoparameres not reaching the apical end of the epiphallic lobes………………… 10 10a. Male genitalia with short endoparameres, and short tapering ectoparameres. . C. gambelae. 10b. Male genitalia with long endoparameres, and short wide ectoparameres. . . . . . . . . . . . . 11 11a. Species less than 12mm in size with an apical field of medium length. . . . . . C. illubabori. 11b. Species larger than 12mm with a long apical field. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12 12a. Ectoparameres with pointed ends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. medvedevi. 12b. Ectoparameres with rounded ends. . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 13a. Pronotum strongly narrowed in front, macropterous female.. . . ……… . . . . . . . C. apricus. 13b. Pronotum not narrowed in front, brachypterous or micropterous female. . . .. . . . . . . . . . 14 14a. Occiput with 3 black bands, the median one being wider, long and the lateral bands narrower, shorter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. desutterae sp. nov. 14b. Occiput with back zone delimited by brown bands extending laterally under each eye to the posterior end of the occiput. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 15 15a. Forewings with a mirror with a dividing vein. . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . .16 15b. Forewings with a mirror without a dividing vein. . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . .19 16a. Male forewings with 4 oblique veins. . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

  16b. Male forewings with 5 oblique veins. .. . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . .18 17a. Occiput with 2 brownish stripes in the black area forming the letter H; Pronotum with many black spots and dots. . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . C. alternatus. 17b. Occiput with 3 short brownish stripes in the black area; Pronotum spotted by a few black dots. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . C. superciliosus. 18a. Division of vein forming a circle with the mirror. . . . . . . . . . . . . . . . . . . . . . . . . C. matuga. 18b. Division of vein forming a triangle with the mirror. . . . . . . . . . . . . . . . . . . . . . . . . C. agilis. 19a. Two broad yellowish bands extending from the head to the tip of the abdomen.. . . . . . . .

  . Coloration more uniform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 20a. Mirror with a short vein indicating the start of division. . . . . . . . . . . . . . . . . .. . . . . . . . .21 20b. Mirror without a short vein to indicate the beginning of division. . . . . . . . . . . . . . . . . . .22 21a. Male forewings with 4 oblique veins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .… . C. duplicatus. 21b. Male forewings with 5 oblique veins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. mombo. 22a. Male forewings with 4 oblique veins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. sagalus. 22b. Male forewings with 5 oblique veins.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. impiger.

Figure 4 .

 4 Figure 4. Numeric temporal fluctuations of Cryncus camerounensis sp. nov. and Cryncus desutterae sp. nov. in forests and fallows of southern Cameroon plateau.

Figure 5 .

 5 Figure 5. Distribution map of African species of the genus Cryncus.

Figure 1 .Figure 2 .Figure 3 .Figure 4 .Figure 5 .

 12345 Figure 1. Location of the sampling localities.

Table 1 :

 1 Characteristics of the Benchmarck village blocks (modified from

Table 2 .

 2 Cryncus camerounensis sp. nov. measurements in millimeters: average ± standard error (minimum-maximun) number of specimens studied Remarks. Cryncus camerounensis sp. nov. differs from other species of the genus by its mirror

Table 3 ). Male holotype's measurements:

 3 BL, 12.09 mm; PL, 1.57 mm; PW, 2.70 mm; FWL, 7.49 mm; ML, 2.67 mm; MW, 1.69 mm; FL, 7.21 mm; FW, 2.86 mm; TL, 4.99 mm. File with 261 teeth.

Table 3 .

 3 Cryncus desutterae sp. nov. measurements in millimeters: average ± standard error (minimummaximun) number of specimens studied.

TABLE 4 .

 4 Frequencies of occurrence of Cryncus camerounensis sp. nov. and Cryncus desutterae sp. nov. as a function of the types of vegetation and localities.

TABLE 5 .

 5 Frequencies of occurrence of Cryncus camerounensis sp. nov. and Cryncus desutterae sp. nov. depending on the capture methods and localities.

Table 1 :

 1 Characteristics of the Benchmark village blocks (modified from[START_REF] Gockowski | Quelques données de l'enquête agricole dans les villages de recherche[END_REF]

	Characteristics of the village blocks of		Sampling localities
	the Benchmark
		Ongot (Yaoundé	Zamakoé	Engout'Adjap (Ebolowa
		bloc)	(Mbalmayo bloc)	bloc)
	Administrative divisions	Mefou and Akono	Nyong and So'o	Mvilla
	Level of forest cover degradation	Degraded	Less degraded	Almost not degraded
	Average age of fallows	3.9 years	5.4 years	7.5 years
	density (inhabitants / km 2 )	14-88 hab/km 2	10-41 hab/km 2	2-15 hab/km 2
	Altitude (m)	810	657	593
	Latitude (North)	03°51'	03°33'	02°42'
	Longitude (East)	011°25'	011°31'	011°03'

Table 2 .

 2 Cryncus camerounensis sp. nov. measurements in millimeters: average ± standard error (minimum-maximun) number of specimens studied Value resulting from the parametric test (t-student). P Value is the probability value. / Missing or absent data.

	Feature Male	Female	t Value	P Value
	BL	13.11 ± 0.76	13.25±0.47	0.16	0.87
		(11.2-14.84) 4	(10.72-16.3) 10
	PL	2.36 ± 0.04	2.51±0.05	1.60	0.14
		(2.29-2.46) 4	(2.27-2.88) 10
	PW	3.67 ± 0.03	3.61±0.07	0.51	0.62
		(3.61-3.74) 4	(3.31-3.95) 10
	FWL	6.84 ± 0.34	3.45±0.12	11.92	5.20×10 ₋08
		(6.14-7.6) 4	(2.72-3.98) 10
	ML	2.71 ± 0.08	/	/	/
		(2.53-2.92) 4
	MW	1.58 ± 0.02	/	/	/
		(1.53-1.62) 4
	CL	6.01 ± 0.67	6.88±0.41	0.88	0.40
		(5.34 -6.68) 2	(5.1-8.78) 10
	FL	9.60 ± 0.27	9.60±0.20	0.05	0.96
		(8.96-10.12) 4	(9.05-10.93) 10
	FW	3.09 ± 0.10	3.31±0.04	2.32	0.04
		(2.84-3.32) 4	(3.14-3.61) 10
	TL	5.93 ± 0.10	6.94±0.20	3.42	0.0045
		(5.68-6.16) 4	(5.83-7.62) 10
	OL	/	10.52±0.32		/
			(7.81-11.37) 10
	FWL	2.90 ± 0.12	1.38±0.05	14.2	7.16×10 ₋09
	PL	(2.68-3.13) 4	(1.2-1.65) 10
	ML	1.71 ± 0.07	/	/	/
	MW	(1.58-1.91) 4
	CL	0.61± 0.04	0.72±0.04	1	0.34
	FL	(0.57-0.66) 2	(0.55-0.95) 10
	OL	/	1.1±0.03	/	/

Table 3 .

 3 Cryncus desutterae sp. nov. measurements in millimeters: average ± standard error (minimummaximun) number of specimens studied

	Feature	Male	Female
	BL	12.09	12.2±1.06
			(11.14-13.26) 2
	PL	1.57	2.21±0.19
			(2.02-2.4) 2
	PW	2.7	3.13±0.05
			(3.08-3.18) 2
	FWL	7.49	6.38±0.76
			(5.62 -7.14) 2
	ML	2.67	/
	MW	1.69	/
	CL	0	(5.47) 1
	FL	7.21	7.42±0.10
			(7.32 -7.53) 2
	FW	2.68	2.33±0.02
			(2.31-2.36) 2
	TL	4.99	5.31±1.11
			(4.2-6.42) 2
	OL	0	8.43±1.57
			(6.86-10.01) 2
	FWL	4.77	2.87±0.09
	PL		(2.78-2.97) 2
	ML	1.58	/
	MW
	CL	0	(0.73) 1
	FL
	OL	0	1.13±0.2
	FL		(0.94-1.33) 2
	Legend: / Missing or absent data.

TABLE 4 .

 4 Frequencies of occurrence of Cryncus camerounensis sp. nov. and Cryncus desutterae sp. nov. as a function of the types of vegetation and localities.

	Species	Localities	Habitats	Total
			Forests	Fallows
	Cryncus	Engout'Adjap	1 (5.26%)	0	1 (5.26%)
	camerounensis	Ongot	1 (5.26%)	0	1 (5.26%)
		Zamakoe	3 (15.80%)	1 (5.26%)	4 (21.06%)

TABLE 5 .

 5 Frequencies of occurrence of Cryncus camerounensis sp. nov. and Cryncus desutterae sp. nov. depending on the capture methods and localities.

	Species	Localities	Capture method	Total
			Pitfalls	Quadrats
	Cryncus	Engout'Adjap	1 (5.26%)	0	1 (5.26%)
	camerounensis	Ongot	1 (5.26%)	0	1 (5.26%)
		Zamakoe	3 (15.80%)	1 (5.26%)	4 (21.06%)
	Total		5 (26.32%)	1 (5.26%)	6 (31.58%)
	Cryncus	Engout'Adjap	0	0	0
	desutterae	Ongot	2 (10.52%)	0	2 (10.52%)
		Zamakoe	1 (5.26%)	0	1 (5.26%)
	Total		3(15.78%)	0	3(15.78%)

Acknowledgements

The authors thank Professor A.V. Gorochov from the Zoological Institute, Russian Academy of Sciences, for his expertise in Cryncus species determination of this study.