Heterocerus tenuis Miller, 1988

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 : 27-28

16. Heterocerus tenuis Miller

( Fig. 22 , 49 , 69 )

Heterocerus tenuis Miller 1988b: 30 .

Description. Length 3.0 - 3.5 mm. General appearance ( Fig. 22 ) and male genitalia ( Fig. 49 ) very similar to those of H. schwarzi ; however, dorsal spine-like projections on either side of the anterior edge of the median plate point outward in the ventral view of the male genitalia.

Diagnosis. Heterocerus tenuis is nearly identical to H. schwarzi and can be separated from this species only through differences in the male genitalia. The dorsal spine-like projections on either side of the anterior edge of the median plate in H. tenuis project laterally in the ventral view ( Fig. 49 ), a character not present in any other member of the undatus group. These two species are not known to be sympatric, but it should be noted that their known ranges are patchy.

Notes. Because H. tenuis and H. schwarzi are nearly identical, the possibility that the two species were synonymous was considered. A comparison of six paratypes of H. schwarzi and 23 paratypes of H. tenuis was made and none exhibited genital characters that could be considered intermediate. The two species appear to be valid.

Distribution. This species is known from Florida, southern Georgia and Rondeau Park, Ontario ( Fig. 69 ). Rondeau Provincial Park is located on a peninsula on the north shore of Lake Erie. The wide gap in the range, and ecology, between the two regions populated by this species, along with Rondeau Parks proximity to some of the major shipping hubs of the St. Lawrence Seaway system, suggests that interstate commerce could have established H. tenuis in this isolated northern locale.

Specimens examined. 16 (See Appendix).

Figures

Figures 21-25. Habiti of Heterocerus species of intermediate size with post-mesocoxal lines. 21) H. schwarzi. 22) H. tenuis. 23) H. undatus. 24) H. texanus. 25) H. collaris. 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.