Discovery of a new soft-bodied click-beetle genus from Namibia with a unique morphology leads to a modified diagnosis of Drilini (Coleoptera, Elateridae)

Abstract

Drilini are soft-bodied predatory click beetles with incompletely metamorphosed females. Approximately 150 described species are distributed in the Afrotropical, Palaearctic and Oriental realms, with the highest diversity known from sub-Saharan Africa. In this study, we describe Namibdrilusalbertalleni gen. et sp. nov. from Namibia which brings the total number of genera in Drilini to 16. The discovery of this unique taxon sheds new light on the diversity and evolution of the enigmatic paedomorphic beetle lineage and is interesting for several reasons. This new species is the only known representative of Drilini that has unidentate mandibles and lacks a hook on the dorsal part of the aedeagal median lobe, two of the few characters heretofore used for the unambiguous identification of members of this group. Furthermore, based on its morphology it belongs to a group of genera (Drilus clade) which heretofore contained only taxa from the Palaearctic Realm. We provide an updated diagnosis of the tribe Drilini, as well as an updated diagnosis and an identification key for the genera of the Drilus clade based on adult males. Further, we explain how to easily recognize adult Drilini from similar-looking soft-bodied elateroids like Elateridae: Omalisinae, Rhagophthalmidae, and Lampyridae: Ototretinae.

Keywords: Afrotropical Realm; Agrypninae; Elateroidea; click beetle; distribution; identification key; male genitalia; new genus; new species; paedomorphosis; taxonomy.

Figure 1.

Namibdrilusalbertalleni gen. et sp. nov., holotype, male A habitus, dorsal view B habitus, ventral view. Scale bar: 4.0 mm.

Figure 2.

Namibdrilusalbertalleni gen. et sp. nov., holotype, male A head with basal antennomeres, dorsal view B head, frontolateral view C head, frontal view D head, ventral view E left antenna, dorsal view. Scale bars: 1.0 mm (A–D); 2.0 mm (E).

Figure 3.

Namibdrilusalbertalleni gen. et sp. nov., holotype, male A head and prothorax, dorsal view B head and prothorax, lateral view C prothorax and mesothorax, ventral view D metathorax, ventral view E apical portion of elytra, dorsal view F right protarsus, dorsal view G left mesotarsus, dorsal view H left metatarsus, dorsal view. Scale bars: 1.0 mm (A, D); 0.5 mm (B, C, E, F–H).

Figure 4.

Namibdrilusalbertalleni gen. et sp. nov., holotype, male A abdomen, ventral view B male genitalia (undissected), dorsal view C abdominal tergites IX and X, dorsal view D abdominal sternite IX, ventral view E male genitalia, dorsal view F male genitalia, lateral view G male genitalia, ventral view. Scale bars: 3.0 mm (A); 0.2 mm (B); 0.5 mm (C–G).

Figure 5.

Representatives of Drilini from the clade D (Drilus clade), adult males in dorsal view ADrilorhinusklimenkoi Kovalev, Kirejtshuk & Shapovalov, 2019, Iran (PCAA) BDrilusflavescens (Geoffroy, 1785), Italy (PCRK) CMalacodrilushajeki Kundrata & Bocak, 2019, Pakistan (PCRK) DMalacogasterpasserinii Bassi, 1834,Tunisia (PCRK). Scale bars: 4.0 mm.