Neocorimus Halstead, 2020

Halstead, David G. H., 2020, New and little known Coleoptera (Silvanidae: Silvaninae) from Central and South America, Insecta Mundi 2020 (842), pp. 1-37 : 6-8

Neocorimus Halstead , new genus

Type species. Neocorimus thomasi Halstead , new species, here designated.

Discussion. Over two decades ago, Dr. Roger G. Booth (NHML) drew my attention to a silvanid from North

Venezuela, a recent accession at the time, that he had identified as representing a new genus near to Acorimus Halstead, 1980 . The latter genus, Corimus Halstead, 1980 , Afrocorimus Halstead, 1980 , and Dentirotacorimus Yoshida et al., 2017 , have somewhat flattened bodies and broad explanate elytral margins and occur in the Old World. The external facies of the specimen from North Venezuela are most similar to those of the currently monotypic African genus, Metacorimus Halstead, 1997 but the genitalia are totally different, the parameres and other structures being most like those found in the New World silvanine Nausibius sahlbergi Grouvelle, 1896 , to which it may be more closely related. Differences between the male genitalia of Neocorimus thomasi and Nausibius sahlbergi are as follows: the parameres of Neocorimus thomasi are relatively longer and slightly narrower than in Nausibius sahlbergi , they have their tooth flange ( Fig. 23, 24 ) on the apical third and the tooth is relatively large, prominent and without an accompanying seta, whereas Nausibius sahlbergi has the flange on the apical quarter and the tooth is associated with a seta; the anterior margin of the median lobe of Neocorimus thomasi has margins curved to an apical point ( Fig. 23 ) but Nausibius sahlbergi lacks a point, the margins being only slightly angled to the apex; also the median strut of Neocorimus thomasi is a little shorter than that of Nausibius sahlbergi . However, external characters, including the presence of deep ventral antennal grooves on the head, the secondary sexual characters of the legs and the general body form of this new taxon are entirely different. Therefore, a new genus is erected here to accommodate this very interesting beetle that perhaps evolved from the same line as N. sahlbergi .

See below for additional morphological comparisons.

Diagnosis. Although similar in general facies to the currently monotypic African genus Metacorimus , the antennae in this new genus have a much more gradually developed club consisting of 5 segments whereas that in Metacorimus is 3-segmented. In Neocorimus (known species) the presumed secondary sexual characters are restricted to the legs (meso- and metatrochanters) whereas in Metacorimus (known species) there is a setiferous pit on the submentum, pro- and mesofemora have prominences and the metatibiae also exhibit secondary sexual characters. In Neocorimus (known species) the last abdominal ventrite lacks a fine marginal line while one is present in Metacorimus . Neocorimus is easily distinguished from similar Old World genera by antennal, tarsal and pronotal characters ( Halstead 1980, 1997).

Description. Characters which seem to have generic significance are as follows:

Body short, depressed and broad, pronotal and elytral margins broadly explanate; head transverse, eyes widely separated dorsally, temple absent (hind margin of head in line with that of eye), antenna with penultimate segment largest, all of basal segment hidden from above by margin of head, 5 apical segments forming very gradually developed club; deep ventral antennal grooves present, which are almost straight and somewhat convergent to front (known species without setiferous pit on submentum of male); pronotum with anterior angles produced in front and lateral limit indicated by indentations, sides probably always without strong teeth (only undulating towards base in known species); femoral line absent; epipleuron very broad, at apex moderately incurved to suture; legs, tarsi simple (without lobed segments), secondary sexual characters present (limited to trochantal teeth in the known species).

Etymology. Greek prefix, neo: new, plus the generic name, Corimus .

Figures

Figures 23–27. Neocorimus thomasi new genus, new species, male holotype, genitalia and associated sternites. 23) Genitalia without internal sac. 24) Paramere, apex enlarged. 25) Internal sac. 26) Sternites 8–9. 27) Sternite 8, part enlarged. Scale lines = 0.2 mm.