Abraeinae

Introduction

Most of the Abraeinae have informally been referred to as the ‘microhisteridae’. This designation indicates the fact that many of the species of the group are tiny, with adults frequently <2mm in length. These include most members of the Abraeini, Acritini, Acritomorphini, and Plegaderini. However, species in the Teretriini and especially Trypanaeinae (still considered a subfamily, although undoubtedly a subordinate member of this group) can be much larger. Altogether this group contains about 500 described species. But given their small size, undoubtedly many remain to be discovered.

Most species of the group are associated in some way with rotting vegetation. Many species are found under the bark of dead and dying trees (especially Plegaderini and Acritini). Many are found in leaf litter. The Teretriini and Trypanaeinae are mainly cylindrical forms associated with the galleries of various woodboring beetles. A few species are known to be associated with ants’ nests. All are predaceous as far as is known.

Characteristics

Abraeinae are diverse in form. The size of the small oval species readily separates them from all other histerids except for the (possibly related) Bacaniini, which also tend to be extremely small. Teretriini and Trypanaeinae are cylindrical in form, ranging from 2-12mm. They can be separated from all other cylindrical histerids by the form of the antennal club, which is basally sclerotized and lacking in annuli (sutures). The principal synapomorphy for the entire Abraeinae is the lack of a separate basal piece of the aedeagus.

Discussion of Phylogenetic Relationships

The relationships among subgroups of Abraeinae are not well understood, due in part to the fact that the tribes and genera themselves are for the most part poorly defined. The one aspect of the tree shown here that is well supported, and somewhat radical, is the placement of Trypanaeinae within the group. Although a relationship close to Abraeinae has been gaining favor (e.g. Lawrence & Newton, 1995; Slipinski & Mazur, 1999), only recently has this been clearly demonstrated on the basis of larval, adult, and molecular data (Caterino & Vogler, 2002).

References

Caterino, M. S., and A. P. Vogler. 2002. The phylogeny of the Histeroidea. Cladistics 18(4):394-415.

Lawrence, J. F., and A. F. Newton. 1995. Families and subfamilies of Coleoptera (with selected genera, notes, references and data on family-group names). Pages 779-1006 in Biology, Phylogeny, and Classification of the Coleoptera: Papers Celebrating the 80th Birthday of Roy A. Crowson (J. Pakaluk, and S. A. Slipinsky, eds.). Muzeum i Instytut Zoologii PAN, Warsaw.

Slipinski, S. A., and S. Mazur. 1999. Epuraeosoma, a new genus of Histerinae and phylogeny of the family Histeridae. Annales Zoologici (Warszawa) 49:209-230.