Medusapyga LaBonte and Maddison, new genus, 2023

LaBonte, James R. & Maddison, David R., 2023, Medusapyga LaBonte and Maddison, a New Genus of Anillini (Coleoptera: Carabidae: Trechinae) from the Pacific Northwest of the United States, Proceedings of the California Academy of Sciences 67 (18), pp. 401-432 : 409-414

Medusapyga LaBonte and Maddison, new genus

Type species. Medusapyga alsea LaBonte, new species , here designated.

Etymology. The generic name refers to the bifurcate setae on laterotergite IX of females. The Latin Medusa alludes to the mythical monster (a gorgon) with snakes rather than hair on her head and the similarity of the beetles’ setae to the forked tongues of snakes, while pyga is derived from the Greek noun pyge for rump, referring to the placement of the setae and that these can often be observed protruding from the posterior of the abdomen. The gender of this name is feminine.

Composition. This genus includes the two species described below.

Recognition. Diagnostic characters of species of Medusapyga include the field of long bifurcate setae on the ventral surface of the apical half of laterotergite IX of the female genitalia, the ventrobasal spine of the male profemur, and the two asymmetrically strongly dilated basal tarsomeres of the male protarsus, the first tarsomere with two rows and the second with one row of adhesive articulo-setae ( Stork 1980) on the venter. Each species has one or more additional unique characters serving to distinguish them from members of previously described genera of North American Anillini . The mesotrochanters of both genders of M. alsea are quadrate, with a large, blunt, triangular tooth along the posterior margin. The profemora of female M. chehalis are distinctly angulate to dentate on the ventrobasal face and males of M. chehalis have a medial laterally compressed and posteriorly declivous keel on ventrite 2 (these species-specific characters will be addressed in more detail under the species descriptions below). Both species are relatively large for North American Anillini , especially M. alsea .

Description. Habitus ( Figs 1 , 2 ). SBL 2.03–2.65 mm. Head large and broad, HW/HL ~0.88, HW/PWm ~0.75–0.81. Pronotum large, broad, PWm/EW ~0.69, with lateral margins sinuate anterior to posterior angles. Elytra convex to distinctly flattened in lateral perspective and ovoid in dorsal perspective, EW/EL ~0.65, EW/SBL ~0.36–0.39. Translucent pale yellowish brown to reddish brown to dark brown.

Dorsal microsculpture imbricate, with the posterior margin of each sculpticell slightly raised. Sculpticell definition distinct but varies between species, among parts of the body, and among portions of those body parts. Sculpticell shape and size similarly variable, with the shape ranging from irregularly isodiametric to elongate irregularly polygonal. Body surface shiny. Dorsum with sparse vestiture of short, fine setae about 0.12–0.25 length of long pronotal and elytral interstrial setae.

Head ( Fig. 7 ). Frontal furrows broadly impressed, parallel, ending well anterior of occiput. Frontolateral carinae distinct and sharply defined, extending from a shelf over the antennal insertions posteriorly to the level of posterior supraorbital setae. A triangular protrusion extends anteriorly between the antennal carinal shelf and the clypeal seta on each side, protruding above the dorsal mandibular articulation and terminating in a small capitation. Using the terms of Sokolov (2016), there are a pair of clypeal setae, a pair of frontal setae, a pair of mediofrontal setae (sometmes represented by only a single seta), two pair of supraorbital setae (with the posterior pair set somewhat mediad of the anterior pair), and a pair of postorbital setae. Eyes absent. Genae with sparse setae of moderate length. Tempora shallowly convex and rounded to obtusely angulate. Occiput set off from the vertex by a shallow transverse depression just posterior of the posterior supraorbital setae. Mentum and submentum separated by distinct suture. Mentum with large, sharply pointed anteromedial tooth, with a pair of long setae near the apex of the medial tooth and lateral and paramedial pairs anterior of the posterior margin. Submentum trapezoidal, with a pair each of long setae anterolaterally near the anterior angles, paramedially, and medially (the shortest), and also with a row of short setae just posterior of the anterior margin. Gula broad, sides slightly convergent posteriorly, sparsely setose.

Mandibles matching basic structure of Bembidion ( Maddison 1993) and Anillini (Sokolov 2013). Stout, with sharp, slightly ventrally curved apices extending well beyond labrum. Each mandible of similar size and shape, except for details of mandibular teeth. Left mandible has terebral (rounded), premolar, and molar teeth. Right mandible has anterior retinacular, terebral, posterior retinacular, premolar, and molar teeth. Labrum rectangular, anterior margin distinctly arcuately emarginate, three pairs of setae (sequentially decreasing in length mediad) along anterior margin. Clypeus trapezoidal, clypeolabral suture distinct, frontoclypeal suture present; with a pair of long posterolateral fixed setae. Subterminal maxillary palpomeres sparsely setose; inner lateral margin of penultimate palpomere strongly arcuate, outer lateral margin straight; terminal palpomere subulate, about one-third as long as penultimate palpomere. Subterminal labial palpomeres sparsely setose; inner lateral margin of penultimate palpomere straight, outer lateral margin strongly arcuate; terminal palpomere subulate, about half as long as penultimate palpomere. Glossa with two apical setae. Distinct, lobate paraglossae extending beyond apex of glossa, each densely setose in the apical half.

Antennae eleven-segmented, robust, antennomeres 4–10 more or less moniliform. Except for scape, all antennomeres at least partially pubescent. Scape stout, oblong, glabrous except for a few scattered setae and four long apical setae; antennomere 2 slightly pedunculate basally, otherwise ovate; antennomere 3 strongly pedunculate, very narrow basally; antennomere 11 elongate oval, narrowest anteriorly.

Pronotum ( Fig. 8 ). Outline cordate, broadest at about one-third total pronotal length from anterior margin and posterior of lateral primary setae, width at anterior slightly greater than at posterior angles. Lateral primary setae about one-quarter of total pronotal length from anterior margin, posterior pronotal setae just anterior of or well anterior of posterior angles. Dorsum with sparse, socketed, small setae. Numerous small setae regularly distributed along lateral margins. Anterior angles rounded. Lateral margins approximately parallel from posterior angles anteriorward, then convergently arcuate to anterior angles, with several small denticles anterior of posterior angles. Posterior margin slightly convex near posterior angles. Lateral explanations distinct and reflexed, widest at posterior angles and abruptly narrowing anterior of posteromedial pronotal impression. Posterolateral depressions inside hind angles deep, short, and ovate, delimiting lateral bounds of posteromedian impression. Disc convex with well defined median longitudinal impression, deepest adjoining anteromedian and posteromedian impressions. Posteromedian impression deep, extending to posterior pronotal margin, deepest at anterior delimitation, otherwise convex throughout.

Scutellum. Small, lateral and posterior margins evenly convex, apex obtusely rounded. Almost entirely within depression anterior of elytral suture. When the pronotum is extended away from the anterior margin of the elytra, as in active, live specimens ( Figs 1 , 2B ) or in most preserved specimens, the scutellum is visible. In live specimens at rest or in some preserved specimens, the posterior margin of the pronotum fits over and against the anterior elytral declivity ( Fig. 2A ), completely concealing the scutellum.

Elytra ( Figs 2 , 9 ). Entire, concealing pygidium. Together elongate oval in dorsal aspect. Each elytron with lateral margin serrulate from humerus to plical crossing. Each elytron lacks basal margination, i.e., no carina from the humerus to the parascutellar seta. Lateral explanation of each elytron distinctly reflexed, narrow, narrowest just posterior of humerus and just anterior of the plical crossing. Each elytron with elytral plica distinctly crossed. Each elytron with five shallow and indistinct striae, only stria 1 complete to apex (although extremely faint in the apical quarter), all others interrupted and ending before elytral apex. Intervals each with a row of sparse, short setae. Elytral apices separately rounded. The elytral lateral umbiculate series consists of nine large setae in “ Type A” arrangement (sensu Jeannel 1963a), with seta Eo9 mesad of margin and forming a geminate pair with seta Eo8 ( Fig. 9 ). Each elytron has a large parascutellar umbiculate seta at the base of stria 2 and a large fixed seta at the apex of stria 2, while stria 3 has three large, socketed setae: one at a level posterad of lateral umbiculate seta Eo3, one at a level anterior of lateral umbiculate seta Eo5, and the last at a level posterad of the geminate pair of lateral umbiculate setae.

Hind wings. Absent.

Legs. Male profemur with large, ventrally directed spine near the base ( Fig. 4A, C ); this spine projects well beyond the ventral face, with its length about two to three times its greatest diameter. Ventral face of male profemur carinate and obtusely angulate from femoral base to spine. Femora sparsely setose, more densely so near apices. Tibiae with basal half sparsely setose, apical half densely setose. Protibia with external apical angle obliquely truncate, apical one-fourth inflexed.

Protarsus with five tarsomeres; basal two tarsomeres of males strongly asymmetrically laterally expanded (both with proximal anterior angle distinctly protruding beyond the anteromedial margin) ( Fig. 5 ); first tarsomere ventrally with two rows of between 4 and 7 adhesive articulo-setae, second tarsomere with one row of about 4 or 5 articulo-setae, both tarsomeres with some of the articulo-setae fused apically ( Fig. 10 ); female basal tarsomeres symmetrical, not laterally expanded, and without ventral articulo-setae.

Abdominal ventrites. Intercoxal process of second visible abdominal ventrite triangular, apex obtuse to acute. Second visible abdominal ventrite longest, about as long as the following two. Apical margin of last visible abdominal ventrite entire, not serrate. Females with two pair of long paramedial fixed setae just anterior of apex of last visible ventrite, males with a single pair. A small shallow fovea, variable among species and sexes, is present on the second visible abdominal ventrite just posterior of the intercoxal process between the metacoxae.

Female genitalia ( Fig. 6 ). Laterotergite IX with many long, bifurcate setae covering much of the ventroapical region. Gonocoxite 2 with a minute ensiform seta and a pair of nematiform setae, one long and the other minute, with the minute seta adjacent to the base of the long seta. Ventrite X slightly sclerotized, forming a single glabrous lobe (visible centrally in Fig. 6 ).

Male genitalia ( Figs 11 , 12 ). Aedeagus of typical form for a carabid ( Fig. 11 ), with basal lobe open dorsally; lacking ventral setae. Parameres of typical form for a member of supertribe Trechitae , with left paramere larger ( Fig. 12 ); both parameres with four apical setae, both without ventral setae.

Figures

Figure 5 (above). Male right pro- tarsi, dorsal view. (A) Medusapyga alsea. (B) M. chehalis. The view of the two specimens is not exactly equivalent, which accounts for some differences between the two images. Scale bars 50 µm.

Figure 6. Female genitalia of Medusapyga alsea from the type locality, ventral view. (A) Overview of voucher V101505. Scale bar 100 µm. (B) Closeup of voucher V101504, showing bifurcate setae on laterotergites. Scale bar 50 µm.

FIGURE 1. (A) Female of Medusapyga alsea from the type locality. (B) Female of M. chehalis from USA, Washington, Thurston Co., 11 km NW of Littlerock, approximately 0.4 km SSW of the type locality, 46.9564°N 123.1366°W, 315 m elevation. Both specimens were freshly killed, and then posed and photographed on soil from their habitats. Scale bars 1 mm.

FIGURE 2. Dorsal habitus. (A) Medusapyga alsea, female. (B) M. chehalis, female. Scale bar 1 mm.

FIGURE 7. Dorsal views of heads. (A) Medusapyga alsea. (B) M. chehalis. Scale bars 100 µm.

FIGURE 8. Dorsal views of pronota. (A) Medusapyga alsea. (B) M. chehalis. Scale bars 100 µm.

FIGURE 9. Left elytron of female Medusapyga alsea, showing fixed setae. Scale bar 100 µm.

FIGURE 4. Left profemora, anterior view. (A) Medusapyga alsea, male. (B) M. alsea, female. (C) M. chehalis, male. (D) M. chehalis, female. Scale bars 100 µm.

FIGURE 10. Ventral surface of basal two protarsomeres of male Medusapyga alsea. Protarsomere 1 is to the left of center, and protarsomere 2 to the right of center. (A) Protar- somere 1 showing two rows of adhesive setae, and protar- somere 2 showing one row of adhesive setae with partially separated apices. (B) From a second specimen, showing the fusion of apices of both rows of adhesive setae on protar- somere 1, and the fusion of apices of all setae on protar- somere 2. Scale bars 25 µm.

FIGURE 11. Male aedeagus, left lateral view. (A) Medusapyga alsea, voucher JRL002. (B) M. alsea, voucher JRL013. (C) M. chehalis, voucher JRL012. (D) M. chehalis, voucher JRL010. Scale bar 100 µm.

FIGURE 12. Parameres of Medusapyga chehalis, voucher JRL012. (A) left paramere, (B) right paramere. Scale bar 100 µm.