Socotrasilis, Geiser, 2017

Geiser, Michael, 2017, First record of the family Cantharidae on Socotra, with description of a new genus and two new species of the subfamily Silinae (Coleoptera: Elateroidea), Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 57, pp. 93-99 : 96-98

Socotrasilis gen. nov.

Type species. Socotrasilis socotrensis sp. nov.

Description. Head with protruding eyes almost as wide as pronotum. Antennae serrate.

Pronotum transversely oval without distinct anterior or posterior angles, its lateral margin with (presumably sexually dimorphic) modifications, its disc more or less evenly convex, without any visible pores, lobes, concavities or tubercles (as found in other Silinae genera).

Claws of each tarsus simple, none cleft, and without basal teeth or lobes.

Elytra very thin and weakly sclerotised, with somewhat leathery texture, their apices individually rounded, leaving a small gap in between, exposing middle part of second-last tergite. Fully winged and with distinct humeral callus.

Last tergite relatively large and protruding. Last ventrite deeply split into two rounded lobes. Aedeagus relatively simple, its outer capsule (composed of what Wittmer refers to as ‘Dorsalschild’ and ‘Ventrales Basalstück’) opened ventrally, not completely covering internal structures in ventral view; with very large, broad and weakly sclerotised median lobe (‘Mittelstück’ in Wittmer’s terminology), and pair of laterophyses behind, other sclerotised structures often found inside aedeagus capsule of other Silinae genera absent. Dorsal shield unusually broad, almost disc-like, subcircular in dorsal view, non-emarginated ( Fig. 7 ).

Differential diagnosis. Distinguished from other genera of the subfamily Silinae by the combination of the following characters: All claws simple and none cleft in male, lacking a basal tooth. Pronotum modified in male, with an emargination and an ear-like lobe in basal half of the lateral margin, but without the additional modifications found in many other Silinae genera. Furthermore, the dorsal shield of the aedeagus is very unusual within the subfamily. The sole known species of this genus resembles some small Indo-Malayan species of Podosilis Wittmer, 1978 and ‘ Silis ’ Charpentier, 1825 sensu lato (i.e. species currently placed in Silis , which do not fit the restricted definition of this genus given by KAZANTSEV (2011) and will have to be transferred to other genera in the future). Both genera have more complex pronotal modifications in males, including multiple lobes, incisions or appendages and pores on the disc ( Silis ); also, they are readily distinguished by their claws. Eusilis Reitter, 1887 , with one known species from Central Asia, also has simple claws, but a very different pronotum (twice as wide as long, widest in basal half, strongly sculptured, and with a pair of deep impressions on the disc and a thin appendage on its lateral margin); also, its aedeagus is of a very different build. The large Afrotropical genus Silidius has one claw of each tarsus cleft in males. Although habitus and pronotum shape show a great deal of variation within Silidius , none of the described species shows much similarity to Socotrasilis . The Palaearctic genera Autosilis Kazantsev, 2011 and Silis (sensu KAZANTSEV 2011) are distinguished by their claws (see WITTMER 1977: figs 1–2 for A. nitidula (Fabricius, 1792)) , pronotal modifications and a different structure of the aedeagus.

Etymology. A combination of the locality ‘Socotra’ and the related genus Silis . Gender feminine (as in Silis ).

Figures

Figs 5–8. Socotrasilis enigmatica gen. et sp. nov. 5 – holotype, dorsal habitus; 6 – male genitalia, ventral view; 7 – male genitalia, dorsal view; 8 – pronotum of male. Scale bars represent 1mm.