Heterocerus undatus Melsheimer, 1844

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 : 25-26

13. Heterocerus undatus Melsheimer

( Fig. 23 , 45 , 66 )

Heterocerus undatus Melsheimer 1844: 98 .

Dampfius undatus (Melsheimer) : Pacheco 1964: 114.

Description. Length 3.2 - 4.5 mm. Brown or reddish-brown. Elytra vaguely trifasciate, limits of pale markings poorly defined; striae absent ( Fig. 23 ). Post-metathoracic coxal lines absent, post-mesothoracic coxal lines present. Male genitalia ( Fig. 45 ) of the H. undatus type; about two times longer than wide; phallobase composed primarily of median plate; posterior two-thirds of median plate gradually expanded anteriorly; anterior third abruptly constricted to about 50% of its greatest width and pointed apically, curved dorsally in lateral view; lateral arms attached to the constricted portion of the median plate and curved outwardly at their anterior ends; anterior two-thirds of dorsal plate ovoid, posterior third with parallel sides; membranous parameres small, pointed and extending from beneath the median plate at its anterior tip; anterior end of median plate and parameres not extending beyond the anterior tip of the lateral arms. Hypermandibulate males unknown.

Diagnosis. Although the general color in this species is often darker than it is in H. collaris , the two species are very similar in appearance and can be distinguished with certainty only by comparing male genitalia. The outwardly curved anterior tips of the lateral arms separate this species and H. collaris from other North American species. Heterocerus undatus is distinguished from H. collaris by the abrupt constriction of the median plate anteriorly, and by the median plate being much shorter (not exceeding the tip of the lateral arms) than that seen in H. collaris .

Notes. One specimen of H. undatus is known from Mississippi. It was collected on the edge of a cultivated field near deciduous forest in Pontotoc County. A flooded ditch was the likely habitat.

Distribution. Heterocerus undatus was previously recorded from the midwestern and northeastern United States into southeastern Canada, as far south as Missouri and Virginia ( Miller 1996). Collection data indicates that H. undatus occurs west into southern Iowa and Kansas, and south into eastern Arkansas and northern Mississippi ( Fig. 66 ).

Specimens examined. 17 (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.