Heterocerus schwarzi Horn

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

15. Heterocerus schwarzi Horn

( Fig. 21 , 48 , 68 )

Heterocerus schwarzi Horn 1890: 11 . Peditatus schwarzi (Horn) : Pacheco 1964: 123.

Description. Length 3.0 - 3.7 mm. Brown or reddish-brown. Elytra trifasciate, pale markings well defined, elytral surface with relatively dense pubescence; striae absent ( Fig. 21 ). Post-metathoracic coxal lines absent, post-mesothoracic coxal lines present. Male genitalia ( Fig. 48 ) of the H. undatus type, slightly more than three times as long as greatest width; body of phallobase dominated by median plate; each third of plate progressively wider anteriorly; anterior edge with a rounded central lobe and a dorsal spine-like projection on either side visible only in lateral view ( Fig. 48 ); lateral arms of phallobase greatly reduced; dorsal plate not distinct, instead dorsal surface with several distinct sclerites; parameres membranous and obscured by a sclerotized plate on the ventral side of the anterior tip of the genitalia. Hypermandibulate males unknown.

Diagnosis. Heterocerus schwarzi is similar to H. texanus and H. tenuis . It generally can be distinguished from H. texanus using external characters if specimens of the two are compared simultaneously; H. schwarzi has elytra with narrower pale markings, a much more punctuate surface and has more pubescence than H. texanus . Heterocerus schwarzi is nearly identical to H. tenuis , and male genitalia must be used to distinguish them. The dorsal spine-like projections on either side of the anterior edge of the median plate point outward and are easily seen in the ventral view of the genitalia in H. tenuis ( Fig. 49 ), but curve dorsally in H. schwarzi and thus are not visible in the ventral view. The ranges of these two species apparently do not overlap.

Notes. This species is rarely encountered in the Southeast. Only one specimen was examined from the study area and was taken along the banks of the Mississippi River in Bolivar County, Mississippi. Additional specimens were seen from two localities along the Mississippi River in Arkansas.

Designation of Lectotype. The Museum of Comparative Zoology (MCZ) at Harvard University inherited the Horn collection from the Academy of Natural Sciences in Philadelphia during the 1960s. The material held by the MCZ was examined and Horn (1890) did not establish a holotype for this species. One specimen was previously labeled as a lectotype although this designation was apparently never published. The male specimen numbered MCZT_32152 (also labeled Lectotype 3271) is here designated as the lectotype of Heterocerus schwarzi Horn. One female specimen with the same collection data and labeled Para-Type 3271.2 is here designated paralectotype. Burnett County, Texas is fixed as the type locality ( Horn 1890).

Labels attached to the lectotype are: Top - Burnett Co Texas, 2 nd- (male symbol), 3 rd - Lectotype 3271 (red), 4 th - H. Schwarzi Horn (hand written), 5 th - M.C.Z. type 32152 (red), 6 th - Aug. - Dec. 2004, M.C.Z. image Database, 7 th - LECTOTYPE Heterocerus schwarzi Horn 1890 , Jonas G. King (red).

Distribution. Heterocerus schwarzi occurs from the northeastern United States, southeast through Indiana into northern Texas, Arkansas, northern Louisiana and western Mississippi ( Fig. 68 ).

Specimens examined. 7 (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.