Trigonochilus macrotarsus Montreuil & Frolov, 2019

Montreuil, Olivier & Frolov, Andrey V., 2019, A review of the Malagasy species of the genus Trigonochilus Brenske (Coleoptera Scarabaeidae: Rutelinae: Adoretini) with description of a new species, Zootaxa 4679 (3), pp. 596-600 : 598

Trigonochilus macrotarsus Montreuil & Frolov , new species

Figs. 1 D–F

Type material. Holotype ♂, “ Madagascar Est, pr. Île de Masoala , m. if, Ambohitsitondrona, 1000m, XII, Vadon et Peyri- eras” ( MNHN) . Paratypes: 1 ♂, 1 ♀, same data as the holotype ( MNHN) ; 2 ♂, 1 ♀, “ Madagascar Est , dct. Sambava, R.N. XII, Marojejy-Ouest, 1600m, XI-59, P. Soga ” ( MNHN) ; 1 ♂, “ Madagascar Est , dct. Sambava, R.N. XII, Marojejy-Ouest, 1300m, IX-X-59, P. Soga ” ( MNHN) ; 1 ♂, 1 ♀, “ Madagascar Est , Massif du Marojejy (rés. nat. intégr. 12), 1300m, 2/ 8- XII-1972, A. Peyrieras ” ( MNHN) .

Description. Holotype, male ( Figs. 1D, E ).

Length 14.0 mm, maximum width 6.5 mm. Head uniformly dark brown, pronotum light brown with 2 dark brown longitudinal stripes; elytra light brown with darker humoral and apical umbones and irregular dark brown stripes; anterior and middle legs light brown, posterior legs darker.

Head. Clypeus broadly rounded, its anterior margin somewhat upturned. Punctures large and rather dense, separated by less than a puncture diameter on disc, each puncture bearing short, laying setae. Frons flat, punctate as clypeus. Frontoclypeal suture distinct. Labrum with a long, dilated medial process. Antennal club elongated, straight, shorter than funiculus and scape combined.

Thorax. Pronotal bordered all around, border narrow. Lateral margins regularly curved, anterolateral angles narrowly rounded, posterolateral angles obtusely rounded. Punctuation somewhat sparser than that on head, punctures bear short and laying setae.

Scutellum . Triangular, punctate, bearing short and laying setae similar to those on head and pronotum.

Elytra. Striae poorly developed, noticeable as rows of punctures, odd interstriae much narrower than even and slightly raised. Punctuation slightly denser on disc, punctures bearing short, laying setae, similar to those on head and pronotum. Lateral margins somewhat crenulate (in dorsal view), with a bit longer and thicker setae in apical third.

Tergite VIII. Moderately convex, prominent, with denser and somewhat longer setae than on elytra.

Ventral side. Metasternum and abdominal sternites with setation similar to that on elytra.

Legs. Protibiae tridentate, basal tooth smaller than 2 basal. Metatibiae and metatarsi enlarged.

Aedeagus. Aedeagus with completely fused parameres ( Fig. 1E ).

Female ( Fig. 1F ). Similar to the male in colour and setation, but have shorter antennae and relatively slender metatibiae and metatarsi.

Paratypes. Body length of the paratypes varies from 12.8–14.5 mm. Coloration of some specimens is lighter with darker stripes on elytra poorly noticeable.

Etymology. The species is named in reference to the highly enlarged metatibiae and metatarsi.

Differential diagnosis. Trigonochilus macrotarsus new species differs from T. oedipus in the following characters: pronotum and head light brown with a pattern of longitudinal darker stripes; anterior and middle legs are light brown, posterior legs are uniformly dark brown; the elytra are more or less parallel-sided; apical margin of labrum with a long, broadened process; metatarsi with two claws in both sexes; aedeagus with parameres split at the apex.

Distribution. Northern Madagascar, Masoala Peninsula ( Fig. 1G ).

The taxonomic position of T. macrotarsus new species within Trigonochilus is provisional. We placed this species in this genus based on the enlarged metatibiae and metatarsi in males similar to those of T. oedipus . However, a number of other characters listed in the diagnoses suggest that the two species may not be closely related or even congeneric. Also close relations of the Malagasy taxa with African ones are not well supported by data. Both African species have the metatibia of males with very long, acute processes on posterior margin ( Arrow 1901; Krikken 1979). Such processes are absent in Malagasy species. Also, the tarsi and claws of the African species are rather slender while those in Malagasy species are much more robust with greatly enlarged apical tarsomeres and claws. Within Malagasy taxa, only T. oedipus shows pointed medial process on labrum, while the new species has a broadened process. Phylogenetic analysis of African and Malagasy Adoretini may suggest establishing another taxon for the Malagasy species or placing them in other nominal taxa. However, until such an analysis is available we follow Ohaus’ classification and consider both Malagasy species with enlarged metatibia and metatarsi within the genus Trigonochilus .

Figures

FIGURES 1A–F. Trigonochilus oedipus (Fairmaire, 1903) (A–C), T. macrotarsus Montreuil & Frolov, new species (D–F) and locality map (G). A, male, dorsal view; B, aedeagus, lateral and dorsal view; C, female, dorsal view; D, male, holotype, dorsal view; E, aedeagus, lateral and dosal view; F, female, paratype, dorsal view; G, locality map (black circle – T. oedipus, white circle – T. macrotarsus). Scale bar = 1.0 mm.