Tropicus pusillus (Say)

King, Jonas G. & Lago, Paul K., 2012, The variegated mud-loving beetles (Coleoptera: Heteroceridae) of Mississippi and Alabama, with discussion and keys to the species occurring in the southeastern United States, Insecta Mundi 2012 (275), pp. 1-53 : 30-31

18. Tropicus pusillus (Say)

( Fig. 26, 27 , 53 , 71 )

Heterocerus pusillus Say 1823: 200 .

Tropicus pusillus (Say) : Pacheco 1964: 137.

Description. Length 2.3 - 3.0 mm. Orange-brown. Elytra orange laterally, with a common brown macula medially ( Fig. 26 ). Males with a process extending from the dorso-lateral edge of each mandible that wraps around the edge of the labrum ( Fig. 27 ), often nearly meeting the process from other side. Postmetathoracic coxal and post-mesothoracic coxal lines absent. Male genitalia ( Fig. 53 ) of the typical Tropicus type, dorsal edge projecting anteriorly.

Diagnosis. Tropicus pusillus can be easily distinguished from all species of southeastern heterocerid by color pattern alone. The elytra are not trifasciate, as they are in southeastern Heterocerus , but have brown sutural margins. Together, these darker margins produce a rather even-edged median macula on the elytra.

This coloration also easily distinguishes T. pusillus from its only southeastern congener, Tropicus nigrellus n. sp., which is entirely black.

Notes. Often the most numerous beetle at a UV light placed near a body of water in the southeastern U.S., T. pusillus is the only species of heterocerid consistently collected from intermittent creek beds, drainage ditches, and sandy ponds. During this project, specimens were collected from the margin of a brackish marshy habitat on the campus of the Gulf Coast Research Laboratory in Ocean Springs, Mississippi.

Distribution. Tropicus pusillus occurs from near the Canadian border south to Panama and Cuba. It was collected in all 63 Mississippi counties where UV lights were run as part of this project, as well as from most Alabama collection localities sampled by Harris et al. (1991, Fig. 39 ).

Specimens examined. 1802 (See Appendix).

Figures

Figures 26-29. Habiti of small southeastern species. 26) Tropicus pusillus. This level of color variation can be seen in either sex. 27) Head of Tropicus pusillus. 28) Heterocerus selanderi. 29) Tropicus nigrellus, holotype male and allotype female. Scale line = 1mm.

Figures 45-53. Male genitalia of southeastern species. The ventral view is shown unless otherwise stated. 45-50) Heterocerus species in the undulatus group. 45) H. undatus. 46) H. collaris. 47) H. texanus; left - ventral view, right - lateral view. 48) H. schwarzi; left - ventral view, right - lateral view. 49) H. tenuis. 50) H. selanderi. 51-53) Augyles and Tropicus species. Figures 52-53 are at roughly 2x relative scale of prior genitalia. 51) Augyles auromicans. 52) Tropicus nigrellus; left - dorsal view, center - ventral view, right - lateral view. 53) Tropicus pusillus; left - dorsal view, right - ventral view.

Figure 66-72. Distribution by county in the United States. 66) Heterocerus undatus. 67) Heterocerus texanus. 68) Heterocerus schwarzi. 69) Heterocerus tenuis. 70) Augyles auromicans. 71) Tropicus pusillus. 72) Tropicus nigrellus.

Figures 32-44. Male genitalia of southeastern Heterocerus species. The ventral view is shown unless otherwise stated. 32-39) Species that lack post-mesocoxal lines. 32) H. fatuus. 33) H. glicki. 34) H. intermuralis. 35) H. angustatus; left - ventral view, right - dorsal view. 36) H. longilobulus. 37) H. pallidus; left - ventral view, right - dorsal view. 38) H. gnatho; left - ventral view, right - dorsal view. 39) H. sandersoni; left - ventral view, center - dorsal view, left - lateral view. 40-44) Species with post-mesocoxal lines. 40) H. sinuosus; left - dorsal view, right - ventral aspect. 41) H. mollinus. 42) H. insolens; left - dorsal view, right - ventral aspect. 43) H. parrotus. 44) H. brunneus.