Heterocerus fatuus Kiesenwetter

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 : 18-20

5. Heterocerus fatuus Kiesenwetter

( Fig. 13 , 32 , 58 )

Heterocerus fatuus Kiesenwetter 1851: 292 .

Neoheterocerus fatuus (Kiesenwetter) : Pacheco 1964: 78.

Description. Length 4.2 - 5.0 mm. Dark brownish-red. Elytra trifasciate; basal and medial pale markings usually broken into series of spots ( Fig. 13 ); striae effaced or feebly indicated. Pronotal disk uniform in color, without pale margins. Post-metathoracic coxal and post-mesothoracic coxal lines absent. Male genitalia ( Fig. 32 ) of the typical Heterocerus type; anterior third of phallobase abruptly constricted to

75% of its greatest width; median plate broadened anteriorly; dorsal plate circular; medial edge of parameres slightly divergent. Hypermandibulate males rare.

Diagnosis. Heterocerus fatuus lacks both mesothoracic coxal lines and distinct elytral striae. They are reddish brown in color and can be confused with H. sandersoni , a species which generally has more noticeable elytral striae. They may be confused with dark specimens of H. pallidus and H. gnatho that lack pale pronotal borders. Based on the apparent difficulty previous workers encountered in correctly identifying this species using external characters only, it is obvious that examination of the male genitalia is necessary for correct placement of specimens. The anteriorly expanded median plate of the phallobase ( Fig. 32 ) will immediately separate H. fatuus from all other sympatric species.

Notes. According to information presented in Miller’s (1996) key, H. fatuus has stronger elytral striae than H. sandersoni . Upon inspection of the male genitalia of a large series of specimens labeled H. fatuus by Miller, it was apparent that the majority of the determinations were incorrect, the misidentified specimens being H. sandersoni .

Specimens of H. fatuus were collected near saline and freshwater bodies of water on Point Clear Island, Hancock County, Mississippi ( Lago et al. 2002).

Distribution. This species is known from scattered records along the Gulf Coast of central Mexico, the coast of New York, and from New Brunswick ( Pacheco 1964). The Point Clear Island specimens mentioned above represent the only reliably identified series of this species known from the Southeast ( Fig. 58 ).

Specimens examined. 26 (See Appendix).

Figures

Figures 11-17. Habiti of large Heterocerus species lacking post-mesocoxal lines. 11) H. pallidus (male is hypermandibulate). 12) H.intermuralis (male is hypermandibulate). 13) H.fatuus. 14) H. gnatho. 15) H.longilobulus. 16) H. sandersoni. 17) H. angustatus.Scale line = 1mm.

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.

Figures 58-65. Distribution by county in the United States. 58) Heterocerus fatuus. 59) Heterocerus sandersoni. 60) Heterocerus intermuralis. 61) Heterocerus angustatus. 62) Heterocerus mollinus. 63) Heterocerus selanderi.64) Distribution of Heterocerus sinuosis by county in Mississippi. 65) Distribution of Heterocerus collaris by county in the United States.