Stenotarsus Perty, 1832

Roubik, David W. & Skelley, Paul E., 2001, Stenotarsus Subtilis Arrow, The Aggregating Fungus Beetle Of Barro Colorado Island Nature Monument, Panama (Coleoptera: Endomychidae), The Coleopterists Bulletin 55 (3), pp. 249-263 : 252-253

Stenotarsus Perty

Taxonomy. Lawrence and Newton (1995) give the most recent classification of the family, placing Stenotarsus in the Epipocinae . Stenotarsus has over 250 species occurring primarily in tropical regions throughout the world. The genus is extremely diverse in morphology, which suggests similar diversity in biology. There are no recent revisions to aid identification in the Americas.

Stenotarsus is readily distinguished from other endomychids by the following set of characters—pseudotrimerous tarsi, with tarsomere II lobed and bearing a dense, spongy mat of setae underneath; antennal club 3­segmented, segments not transverse; pronotum with broad, flat lateral bead; body distinctly pubescent, pubescence frequently dense, usually uniformly red­brown; body occasionally with a large black area on each elytron and the pronotum. Strohecker (1953) presents a key to the subfamilies and genera of the World’s Endomychidae . Since then, numerous taxonomic reorganizations have occurred. The first description of Stenotarsus larvae is in McHugh and Pakaluk (1997) based on two Australian taxa. Larvae of most Stenotarsus remain unknown. Published descriptions of adult beetles are brief and generally uninformative, unless one is familiar with the genus. Species identifications are based primarily upon comparison with properly identified material, and revisionary work is needed.

Useful characters exist for identifying species of Stenotarsus , for example sexual dimorphism, the shape and color of antennomeres, body size and shape, vestiture color and density, and male genitalia. Species also are distinguishable by the presence or absence of black marks on the pronotum and elytra. Comparision of characters indicates that these marks are somewhat variable within a population, or are clinal (see following Remarks of Stenotarsus ovalis Arrow and S. panamanus Gorham ). Not all species display sexual dimorphism, how­ ever. Males of some species can possess any of the following sexually dimorphic characters: spur on the metatrochanter (Tanaka 1986) or metafemur; metatibia modified, curved, with or without internal tubercles; metasternum with various structures on the anterior edge between the mesocoxae, usually a depression of some definable shape; abdomen sometimes with a dense patch of setae on one or all sternites. In addition, there can be different body and appendage proportions (Nedved and Windsor 1994 b). These dimorphisms are present in various combinations and degrees between species, and frequently offer the best characters for identification. Females of many species that lack such characters often are impossible to identify without an associated male.

Many species of Stenotarsus occur in Panama. We were unable to identify some of the material available for study, and left these specimens for future work. The following key to eleven Panamanian species includes only those with published records, or specimens identified by Strohecker.