Medusapyga chehalis LaBonte, 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 : 418-419

Medusapyga chehalis LaBonte , new species

Holotype. Male, deposited in the California Academy of Sciences , labeled: “ WASHINGTON, Thurston Co., 11.3 km NW Littlerock, elev. ~ 400 m, D.J. Cox and J. R. LaBonte, 6 May 2007, 46.9600°N 123.13450°W ”, “ HOLOTYPE, Medusapyga chehalis LaBonte sp. nov., designated 2022 [red paper]”.

Paratypes. 59 (32 females, 27 males), residing in the following collections and institutions: CAS (4), CMNH (2), CNC (2), JRLC (39), LACM (2), MCZ (2), NHMUK (2), OSAC (4), WSU (2). USA, Washington, Thurston Co., 9.5 km NW of Littlerock, Falls Creek Campground, 46.9333°N 123.1333°W, 200 m elevation, 30 IV 2000, J. Longino (2) (#4212, ENT 145103 LACM). USA, Washington, Thurston Co. , 11.3 km NW of Littlerock, 46.96000°N 123.13495°W, between 366–412 m elevation [Type locality]. 6 V 2007, D.J. Cox and J. R. LaBonte (4). 12 V 2007, J. R. LaBonte (7). 23 V 2007, J. R. LaBonte (6). USA, Washington, Thurston Co. , 11 km NW of Littlerock, 46.9564°N 123.1366°W, 315 m elevation, 2 IV 2022, J. R. LaBonte (4). USA, Washington, Thurston Co. , 9.3 km NNW of Littlerock, 46.9620°N 123.1084°W, 301 m elevation, 28 IV 2014, J. R. LaBonte (27, 8 of which were extracted from soil and litter) – D.H. Kavanaugh and J. R. LaBonte (4). 22 IV 2021, J. R. LaBonte (3, all of which were extracted from soil and litter) .

Depending upon the GPS system used, the exact geographic coordinates and elevations may slightly differ among the labels of the different collectors and institutions.

Type Locality. USA, Washington, Thurston Co., 11.3 km NW of Littlerock, 46.9600°N 123.1350°W, elevation ~ 400 m.

Etymology. The specific epithet refers to the southwestern Washington river drainage of this name and a community near the type locality. The name is to be treated as a noun in apposition.

Description. Habitus ( Fig. 2B ). SBL 2.03–2.35 mm. Color translucent testaceous to dark brown. Flattened in lateral view.

Head ( Fig. 7B ). The medial convexity formed by the frontolateral furrows does not end in a frontoclypeal prominence as in M. alsea but instead gradually and evenly decreases in elevation anteriorly. Tempora obtusely angulate.

Pronotum ( Fig. 8B ). PWm/ PL ~1.30, PWa/PWp ~1.10. Widest at about anterior quarter, posterior of insertion of large anteriolateral setae. Anterior angles rounded and, as essentially a continuation of the slightly arcuate and emarginate anterior margin, protrude only slightly beyond the anteromedial margin. Lateral margins slightly sinuate, approximately parallel only just anterior of posterior angles, oblique to greatest pronotal width, then convergently arcuate to anterior angles. Lateral explanations distinctly narrowly reflexed, width more or less uniform throughout except broadened posterior of posteromedial impression, widest at hind angles. Hind angles right to slightly obtuse, rounded, anterior of posterior margin. Width at posterior margin less than at hind angles. Lateral margins with fine serrations at and just anterior of hind angles, extending to posterior margins of hind angles. Disc not as strongly convex as in M. alsea . One long, stout seta well anterior of each posterior angle (at approximately the anterior delimitation of the posteromedian impression) and a longer seta located laterally at approximately the anterior seventh of each side.

Elytra ( Fig. 2B ). Greatest width at mid-length. Slightly convex in lateral view, shallowly ascending from anterior margin to about anterior third, thereafter very shallowly and evenly descending to apex, more or less evenly and slightly convex in cross section. Each elytron with lateral margin finely denticulate from humerus to plical crossing. Humeri arcuate and obtusely round- ed. Lateral margins slightly arcuately posteriorly divergent in anterior half, thereafter lateral margins evenly convergently arcuate to the separately rounded apices. Only very faintly indented at the plical crossing. Intervals flat.

Legs. Profemoral spine of males near basal one-sixth of ventral face, with its length about

twice its greatest diameter ( Fig. 4C ). Females lack the elongate profemoral spine of males; however, in the same position they have a distinct obtuse angulation that can vary in expression to a short denticle ( Fig. 4D ). Females also have a carina extending from the profemoral base to this angulation, similar to that found in males. Mesotrochanter with posterior margin more or less evenly arcuate (Fig. 13B).

Abdominal ventrites. Apex of intercoxal process of second visible abdominal ventrite obtuse. There is a very small, shallow fovea on this ventrite just posterior of the intercoxal process between the metacoxae. It is in the shape of a broad trapezoid narrowest at the anterior and broadest at its posterior. The surface of the fovea is coarsely punctate.

In males there is a small medial laterally compressed carina (the “keel”) located at about slightly more than 1/5 the total length of visible abdominal ventrite 2 from the posterior FIGURE 15. Known geographic distributions of Medusamargin thereof (Fig. 14A). This keel is tallest pyga alsea (star) in Oregon and Medusapyga chehalis (circle)

in Washington. at its posterior extent and is an elongate triangle in lateral perspective (Fig. 14B). It is most often sharply pointed (slightly rounded in a few males) at the tallest point and is perpendicularly declivous to the plane of the ventrite.

Male genitalia ( Fig. 11C, D). Aedeagus with ventral margin somewhat sinuate, less arcuate than M. alsea , with subapical downward bulge. Internal sac with small dark structure near dorsum.

Sexual dimorphism. In addition to the differences in protarsomeres and profemora, and lack of a medial preapical keel on visible abdominal ventrite 2, females are larger than males. Female SBL ranged from 2.13–2.35 mm and averaged 2.25 mm. Male SBL ranged from 2.03–2.18 mm and averaged 2.10 mm. A two-tailed Student’s T-test indicated these differences in average length were highly significant (p = 0.0000003). The abdominal fovea on visible abdominal ventrite 2 is much longer and broader in females, about 1/3 the length of ventrite 2 from the metacoxae to the ventrite’s posterior margin. It is 2.4 times as long as the male fovea. The female fovea is also much more deeply impressed. It is almost circular, about as wide as long.

Variation. The posterolateral pronotal margins immediately anterior of the posterior margin of some specimens were slightly obliquely divergent, rather than parallel. Although most specimens were pale testaceous, a few specimens were very dark brown, almost black. A few of the paler individuals may have been teneral; this appears certain for a male with a clearly teneral aedeagus.

Identification. Characters of M. chehalis distinguishing it from M. alsea include smaller average length, depressed and less robust habitus, absence of a frontoclypeal prominence, pronotum without protruding anterior angles and with obtuse and rounded posterior angles, females with angulate to faintly denticulate profemoral bases, mesotrochanters with evenly rounded posterior margins, punctate abdominal foveae, and with a less arcuate aedeagus lacking a C-shaped structure in the internal sac.

Geographic distribution (Fig. 15). M. chehalis is known only from four closely proximate sites: Falls Creek Campground at 46.9333°N 123.1333°W and 200 m elevation, the type locality approximately 2.0 km to the north at 46.9600°N 123.1350°W and between 366–412 m elevation, a site approximately 0.4 km SSW of the type site at 46.9564°N 123.1366°W and 315 m elevation, and a site approximately 2.6 km east of the type locality at 46.9620°N 123.1084°W, at 301 m elevation, all in southwestern Washington. None of these sites are farther than 2.6 km apart and bound a roughly triangular area of about 270 hectares .

Figures

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 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.