Agathidium dentigerum Subgroup

MILLER, KELLY B. & WHEELER, QUENTIN D., 2005, Slime-Mold Beetles Of The Genus Agathidium Panzer In North And Central America, Part Ii. Coleoptera: Leiodidae, Bulletin of the American Museum of Natural History 2005 (291), pp. 1-167 : 130

Agathidium dentigerum Subgroup

DISCUSSION: This group of species is characterized by the operculum of the median lobe completely divided into two long, independent rami (e.g., fig. 309), extensive endophallic armature consisting of an elongate medial, triramous process with a medial, apically truncate lobe and lateral, flattened hyaline lobes, the base of the lateral lobes distinctly sinuate in ventral aspect (e.g., fig. 309), relatively narrow metasternum medially with moderately large male metasternal fovea, somewhat reduced eyes that are dorsoventrally compressed and ovoid with large facets, and a large, acutely pointed, occasionally somewhat falcate male metafemoral tooth. The group may be further divided into two groups based on the presence or absence of a prominent lobelike tubercle medially on the gula. Other than this, the species are very similar externally with the only other significant differences being the relative development of the medial mesosternal and oblique metasternal carinae and the development of the lobelike process posteromedially on the metasternum. Male genitalia are generally diagnostic and male specimens should be dissected for most positive identification of specimens. The species are eastern Nearctic in distribution. They have been most commonly collected by sifting various litter types and Berlese extraction. The reduced eyes, strong contractility, and winglessness of many specimens suggest they are cryptic in habitats living in litter and in the substrate.

The only previously described species in this group is A. dentigerum Horn. Since the species in this subgroup are externally very similar, it is not surprising that Horn (1880) apparently included specimens in A. dentigerum that belong in what we describe here as new species. As additional collecting in the eastern United States ensues, we expect more species of this subgroup to come to light since the species appear to be numerous, cryptic in habitat, and relatively poorly collected.