Adelothyreus brevis Otto, Muona and Córdoba-Alfaro, 2023

Otto, Robert L., Muona, Jyrki & Córdoba-Alfaro, Jim, 2023, A new genus and sixteen new species of false click beetles (Coleoptera: Eucnemidae) described from the Heredia Province of Costa Rica with several additional records from the Osa Peninsula and Panama, Insecta Mundi 2023 (991), pp. 1-36 : 7-8

Adelothyreus brevis Otto, Muona and Córdoba-Alfaro , new species

Figures 10–12

Diagnosis. The presence of a very short anterior lateral pronotal ridge will distinguish the new species from all known Adelothyreus species present in Costa Rica.

Type material. Male holotype: “ COSTA RICA: Heredia; Est.Bio. La Selva , 50–; 150 m 10°26′N 84°01′W; Proy. ALAS, INBio-OET” / “M/06/085; 02 Mayo 1993; Bosque primario” / “ HOLOTYPE:; Adelothyreus ; brevis ♂; Otto, Muona & Córdoba-Alfaro; Det. R. L. Otto; 2019” (red printed label). Holotype to be deposited in INBC.

Description. Male holotype: Length, 2.5 mm. Width, 0.50 mm. Body elongate; uniformly dark black; antennae dark brownish black; legs dark brown; head, pronotum and elytra clothed with short, recumbent yellowish setae ( Figure 10). Head: Surface densely punctate, somewhat dullish, subspherical; frons convex, without median fovea or carina; apical margin of frontoclypeal region rounded, more than 2.0 times wider than base; mandibles stout, bidentate, densely punctate. Antenna: Pectinate from flagellomeres III–VIII, attaining about 2/3 the length of the body; flagellomere I longer than II; flagellomere II strongly, asymmetrically serrate; flagellomeres III–IV longer than wide, sub-equal, each shorter than V; flagellomeres V–VIII each sub-equal, longer than wide; flagellomere IX longer than VIII; rami on flagellomeres III–VIII arising at apical end, short and about as long as the length of the segment. Pronotum: Surface somewhat dullish, closely punctate; longer than wide, with poorly developed hind angles; lateral sides parallel-sided, laterally sinuous above pronotal hind angle, apically arcuate; disc flattened without median groove; anterior lateral pronotal ridge extremely short, directed posteroventrally; posterior lateral pronotal ridge elongate, extending at least 3/4the length of pronotum ( Figure 11); base sinuous, with circular strong impressions above scutellar shield. Scutellar shield: Quadrate, sub-triangular, shallowly punctate, setose and distally rounded. Elytra: Striate indistinct; interstices flattened; surfaces shiny, closely punctate to rugose at basal 1/2, shallowly and closely punctate at apical 1/2. Legs: First tarsomere as long as the combined lengths of the remaining four on meso- and metatarsi; tibiae rounded in cross section; metatarsomeres I–III simple; metatarsomere IV very short, excavate; metatarsomere V short with simple claws. Venter ( Figure 12): Closely punctate, with short, recumbent yellowish setae; hypomeron with apically widened notosternal antennal grooves; antennal grooves smooth, scarcely punctate apically; metepisterna caudally wide; elytral epipleura punctate; metacoxal plates parallel-sided.

Distribution. This eucnemid species is known only from its type location in Costa Rica

Biology. The holotype was taken from a primary forest. Larvae and pupae are unknown.

Etymology. The specific epithet is derived from the presence of a very short anterior pronotal lateral ridge.