Liocosmius Casey, 1918

Maddison, David R., 2023, A New Subgenus of Bembidion Latreille from México and Guatemala, with Descriptions of Two New Species (Coleoptera: Carabidae), Proceedings of the California Academy of Sciences 67 (19), pp. 433-450 : 445-446

Subgenus Liocosmius Casey

Type species Ochthedromus mundus LeConte (1852) , designated by Lindroth (1963).

A revision of Liocosmius is provided in Maddison and Cooper (2014). The species described here as Bembidion cachagua became known shortly before the publication of that work, but it was not recognized as a Liocosmius until after a genitalic dissection and DNA sequencing revealed that it belonged to the subgenus. Within Liocosmius , B. cachagua is unusual for its microsculptured pronotum and head, rugose pronotum (at least in the posterior portion), low-contrast color pattern on the elytra, and slight metallic sheen on elytra. The species can be identified in the key provided by Maddison and Cooper (2014) if an additional couplet is added at the beginning:

0. Evident microsculpture throughout dorsal surface of head (except, in some specimens, between eyes near midline), and over most of the pronotum; microsculpture near apex of elytra evident as distinct sculpticells that are only slightly transverse. Ground color of elytra brown, slightly depigmented, contrasting only weakly with pale spots ( Fig. 7A ). Entire dorsal surface with slight yellow-green or brown-green metallic sheen, including on the elytra. Appendages infuscated. Posterior region of pronotum evidently wrinkled, at least medially, and with many punctures ( Fig. 7B )............................ B. cachagua sp. nov.

— Most of the dorsal surface of head without microsculpture; pronotum with at most weak, very transverse microsculpture restricted to lateral margins; microsculpture absent from apex of elytra or consisting of very transverse sculpticells. If ground color of elytra brown and contrasting only weakly with pale spots, then appendages testaceous, not infuscated ( Maddison and Cooper 2014, Fig. 2 ). Elytra without metallic sheen. Posterior region of pronotum smoother (e.g., Maddison and Cooper 2014, Fig. 7 )............................... 1

Figures

FIGURE 7. Holotype of Bembidion cachagua. (A) Habitus, scale bar 1 mm. (B) Forebody, scale bar 0.5 mm.

FIGURE 2. Geographic distribution of Geocosmius in México and Guatemala.