Revision of the species of Chaetocnema from Madagascar (Coleoptera: Chrysomelidae: Alticinae)

The species of ilea beetles of the genus Chaetocnema Stephens, 1831 occurring in Madagascar are revised. Four new spe­ cies (C. cachani, C. hygrophila, C. malgascia and C. orophila) are described and five species (C. bamakoensis Bechyné C. confinis Crotch, C. fiuscipennis Scherer, C. ganganensis Bechyné and C. picipes Stephens) are added to the Madagascar fauna. The following new synonymies are proposed: C. wollastoni Baly, 1877 = C.firaterna Harold, 1879 syn. nov. = C. monomorpha Bechyné, 1964 syn. nov.; C. pulla Chapuis, 1879 = C. tantilla Weise, 1910 syn. nov.; C. bilunulata Demaison, 1902 = C. sylvia Bechyné, 1964 syn. nov.; C. vadoni Bechyné, 1948 = C. alaotrensis Bechyné, 1964 syn. nov.; C. gregaria Weise, 1910 = C. insularis Weise, 1910 syn. nov. Lectotypes are designated for C. gregaria Weise, 1910, C. insularis Weise, 1910, C. similis Weise, 1910 and C. tantilla Weise, 1910.A key to all the species is presented. Line drawings of male and female genitalia of all the species are included. Ecological and brief zoogeographical data on some species are given.


INTRODUCTION
The first records of Chaetocnema Stephens, 1831 in Madagascar are those of Baly (1877) and Harold (1879), who described C. madagascariensis and C. fraterna, respectively.About thirty years later, Weise (1910) made an important study of the leaf beetles of Madagascar and the Comoro Islands, and described five new species in this genus (C. consobrina, C. gregaria, C. insularis, C. tantilla and C. similis).As part of his study on the Mada gascar leaf beetle fauna, Bechyné (1948Bechyné ( , 1964) ) described additional species of Chaetocnema (alaotrensis, basipunctata, coronilla, monomorpha, pauliani and syl via).Finally, additional data on some Chaetocnema spe cies occurring in Madagascar were reported by Scherer (1962a).
In the present paper all Chaetocnema species known from Madagascar are critically revised.Some species are reported for the first time and others synonymized.Moreover, four new species are described (C. cachani, C. hygrophila, C. malgascia and C. orophila).For each taxon, type material was examined.Finally, the distribu tional data are updated, taxonomy discussed, male and female genitalia described, and ecological information given.The Madagascar locality names used in this paper, follow those ofViette (1991).

Chaetocnema basipunctata Bechyné
Chaetocnemabasipunctata Bechyné, 1964:  Comments.C. basipunctata is the most uncertain spe cies of Chaetocnema occurring in Madagascar.Its sys tematic affinities are unknown because it shares morpho logical characters with several species-groups.For exam ple, on the basis of the presence of a narrow frontal carina, especially in the male, C. basipunctata is similar to the species in the subgenus Tlanoma Motschulsky, 1845 (represented in Madagascar by the species bilunulata, confinis, picipes, malgascia n.sp.andpulla); on the basis of the line of well impressed punctules present on the pronotal base and the very weak punctation on the vertex of the head this species is similar to species of the gregaria species-group (represented in the Madagascar fauna by the species gregaria, cachani n.sp., madagascariensis, orophila n.sp., and vadoni); finally on the basis of the shape of the male and female genitalia (Figs 16,37) it shows clear affinities with the Afrotropical species such as C. kibonotensis Weise, 1910 widespread in Cen tral and Southern Africa (personal data), or Asiatic spe cies relatedto C. hortensis (Geoffroy, 1785).
Bionomics.Species associated with Gramineae in open fields (cf.Scherer, 1962b;Tiberghien, 1976).Comments.In comparison with the specimens of C. bilunulata from Continental Africa, the specimens from Madagascar more frequently show uniform blackish colouration on the elytra.Chaetocnema cachani n. sp.
Pronotum moderately transverse (LP = 0.64 mm; WP/LP = 1.49), slightly wider at base, laterally almost straight; lateral and basal margin very distinctly bordered; anterior angles thickset, apically rounded, with a small setigerous pore; punctation very weakly impressed on clearly microreticulate surface; pronotal base with an evi dent line of punctules.
Hind femora dark brown; anterior and middle femora partially darkened; tibiae and tarsi reddish; hind tibiae with lateral dilation acute and apical spur short and red dish; 1st anterior and middle tarsomere very weakly dilated, subtriangular.
Ventral part dark brown with weak metallic reflection.Last sternite with sparse punctules on an almost smooth surface; special preapical impressions absent.
Comments.Relative to the populations of C. ganganensis occurring in Continental Africa, the Madagascar specimens have no or only weak microretuiculation on the pronotal surface.Moreover, this species is very similar to C. sundara Maulik, 1931 from the Seychelles, from which it is distinguished by having more convex lat eral elytral interstriae, more rugose punctation on the head and pronotum and a more strongly curved median lobe of aedeagus in lateral view.
All femora distinctly blackened with evident metallic reflection; tibiae and tarsi partially but clearly darkened; hind tibiae with obtuse lateral dilation, and reddish and very short apical spur; 1st anterior and middle tarsomere clearly dilated, subtriangular.
Ventral part black with weak metallic reflection.Last sternite with sparse but well impressed punctation; sur face almost smooth; special preapical impressions absent.
Median lobe of aedeagus (Fig. 20) moderately slender (LAED = 0.83 mm; LE/LAED = 1.77); in ventral view apically rounded with and evident median truncate small tooth; ventral sulcus narrow but clearly impressed; median lobe in lateral view moderately and regularly curved.
Paratypes  Etymology.The name of this new species refers to the fact that it is found in moist environments.

Bionomics.
No ecological information is available for this species.examined this type specimen, which is unfortunately almost completely destroyed but for a little of the ventral parts and the legs, which are not useful for the identifica tion of the species.In the entomological collections of the MNHN I found two specimens (male and female) that fit very well with the original description of C. madagascariensis.These specimens are briefly described.Dorsal integument blackish with an evident metallic bronze reflection, especially on pronotum.Body shape elongate, with pronotum and elytra laterally subparallel.Antennae basally pale; interantennal space wide and impunctate.Head and pronotum finely but densely punctate; surface clearly microreticulate.Pronotum with anterior angles distinctly raised, apically slanted; pronotal base deeply bordered with a line of well impressed punctules.Elytra entirely covering pygidium; interstriae with sparse fine punctules; humeral callus evident; macropterous.Tibiae and tarsi reddish; anterior and middle femora partially darkened; hind femora blackish.
Of the Chaetocnema species occurring in Madagascar, C. madagascariensis is very close to C. cachani n. sp., but it is easily distinguished by the characters given in the key.Chaetocnema malgascia n. sp.
Hind femora blackened with evident metallic reflection; anterior and middle femora darkened; tibiae and tarsi mostly pale; hind tibiae with lateral dilation very acute and very elongate reddish apical spur; 1st anterior and middle tarsomere elongate and moderately thickset.
Ventral part entirely piceous with weak metallic reflec tion.Last sternite distinctly punctulate with almost smooth surface; special preapical impressions absent.
Diagnosis.This species is attributed to the subgenus Tlanoma Motschulsky, 1845 and occurs in Madagascar along with the widespread species bilunulata, confmis, picipes and pulla.However, C. malgascia n. sp.shows the closest affinities with Oriental species such as the Asi atic C. discreta (Baly, 1877), from which it is distinguish able mainly by the shape of the median lobe of the aedeagus and spermatheca.Etymology.The name of this new species refers to where it was first found, Madagascar.Distribution.Madagascar.Bionomics.No ecological information is available for this species.
Ventral part mostly piceous with very weak metallic reflection.Last sternite with subrugose surface; special preapical impressions absent.
Diagnosis.This new species is close to other Mada gascar species such as C. vadoni, C. cachani, and C. madagascariensis, but it is easily distinguishable by the smaller size, the pronotum comparatively more transverse and the different shape of median lobe of aedeagus and spermatheca.
Bionomics.Species associated with Gramineae (cf. Tiberghien, 1976;Furth, 1985).CONCLUSIONS As reported above, at least 20 species of the genus Chaetocnema occur in Madagascar.The possible coloni zation routes of these species are given in Fig. 42.This scheme is based on preliminary results of a phylogenetic study on the groups of species of Chaetocnema now under preparation.
As expected, the endemism rate is rather high; that is notwithstanding that the species of this genus are gener ally macropterous and so potentially good dispersers, which generally limits local endemism.The endemic spe cies of Chaetocnema in the Madagascar make up about 55% of the total.
The other Chaetocnema spp. in the Madagascar fauna can be subdivided into: -vagrants: widespread species that very probably dis persed naturally from Continental Africa to Madagascar (C. bamakoensis, C. bilunulata, C. fuscipennis, C. ganganensis, C.pulla, C. wollastoni); -aliens: species possibly introduced by man and mainly associated with the cultivation of exotic crop plants.This is surely the case for C. confinis Crotch associated with sweet potato and C. picipes Stephens associated with soy bean.
At present little is known about the Madagascar flea beetle fauna.Future investigations will definitely add new taxa and a significant amount of new data about the local distribution of species.For example, looking at the distri butional maps (Fig. 41), it is clear that most Chaetocnema species in Madagascar are from the eastern part of the island.This partly due to the richness of the moist envi ronments in this area (very important for almost all spe cies of this flea beetle genus) and partly due to being the most investigated.In contrast little data exist for the western part of Madagascar, which is more xeric with extensive deciduous forests and shrubbery (cf.Du Puy & Moat, 1996).

Fig. 41 .
Fig. 41.Distribution maps of the Chaetocnema species in Madagascar and Comoro Islands.