Pensus Halstead, 1973

Halstead, David G. H., 2020, New and little known Coleoptera (Silvanidae: Silvaninae) from Central and South America, Insecta Mundi 2020 (842), pp. 1-37 : 13-14

Pensus Halstead

Pensus Halstead 1973: 77

Discussion. Pensus was erected by the author to accommodate two species previously placed in Silvanus , Silvanus gilae Casey (1884: 72) and Silvanus guatemalenus Sharp (1889: 560) . The general appearance of the genus is similar to that of Silvanus , but Pensus differs in that antennomere 8 is much smaller than both antennomeres 7 and 9 ( Fig. 41 ), whereas in Silvanus it is only slightly smaller than 7. In addition, and of particular importance, Pensus males have genitalia with the median lobe apically rounded, not terminating in a small or large point as in Silvanus , and parameres that are not forked apically as they are in Silvanus .

Several years after creating a new genus for the two described species, a single male of a new one was discovered amongst undetermined silvanids received from the CAS collections. This species has longer, much more obvious pubescence than the two already allocated, and unlike them, it lacks setiferous ocellate punctures (i.e., punctures are without a raised margin) on the head and pronotum (compare Fig. 40 with Fig. 47 and 50 ). Comparatively recently, Dr. M. C. Thomas (FSCA) sent two females of the new species collected by his colleagues, and an additional six specimens, including both sexes, on behalf of R. S. Zack (WSU). Habitats for members of the genus on data labels include “Under bark of log”, “oak forest” and “under the bark of Quercus guatemalensis”. Some of the specimens were collected in the cloud forests of Guatemala.

Important external characters for distinguishing the three species of Pensus so far known are provided by the form of the dorsal punctures and the length of their setae (this character separates P. hirtus from the other two), also the presence of small temples in contrast to their virtual absences (this character separates P.gilae from P. guatemalensus ). Other external parts, including eye size and pronotal shape can vary. In the latter case the sides may be straighter and more parallel than illustrated here ( Halstead (1973) includes additional illustrations for P.gilae and P. quatemalensus ). Thus, although indicative these other parts are too variable to be used alone in determining species. The male genitalia, in particular the parameres, are of value in confirming identifications.

The new species is described below followed by a key for the identification of the three known species.

Figures

Figures 39–45. Pensus hirtus, new species. 39) Habitus. 40) Part of head enlarged to show, eye, temple, part of puncturation and pubescence. 41) Antenna, enlarged. 42–45) Male genitalia and associated sternites. 42) Genitalia without internal sac. 43) Paramere, enlarged. 44) Median lobe, enlarged. 45) Sternites 8–9. Scale lines for Figure 39 = 1.0 mm, for Figures 42 and 45 = 0.2 mm.

Figures 46–51. Pensus spp. 46–48) P. gilae (Casey). 46) Habitus. 47) Part of head enlarged to show, eye, temple, part of puncturation and pubescence. 48) Genitalia, paramere with variants of lateral prominence inset. 49–51) P. guatemalenus (Sharp). 49) Habitus. 50) Part of head enlarged to show, eye, temple, part of puncturation and pubescence. 51) Genitalia, paramere and median lobe. Scale lines for Figures 46 and 49 = 1.0mm, for Figures 48 and 51 = 0.2 mm.