Most aleocharines can be recognized by antennae that are inserted posterior to a line drawn along the anterior margins of the eyes (Fig. 1.13.1), non-bulging eyes (unlike Steninae), male genitalia with complex parameres and their overall appearance which is unlike that of the Scaphidiinae (Fig. 1.1.1). The following two aleocharine groups of ECAS are exceptions, because their antennae are inserted either anterior to the level of the anterior eye margin or ambiguously close to it:

• Trichopsenius Horn, with characteristic metasternal plates (Fig. 1.13.2) and a distinct habitus (Fig. 1.13.3)
• The tribe Hypocyphtini, minute beetles (<2mm) with only 10 antennomeres (Fig. 1.13.5)

Aleocharinae is the most diverse subfamily of Staphylinidae in ECAS and also the least known. This subfamily is widely distributed in North America and occurs in almost all terrestrial habitats, but most species are forest dwelling. There they occur in leaf litter, under bark, in fungi, in moss and within the nests of ants, termites, mammals and birds. Elsewhere in ECAS they inhabit seashores, edges of water bodies, wetlands and prairies. Drusilla canaliculata Fabricius is a common species often found in disturbed areas under leaves and stones, usually near ants but often near water (Fig.9.1.1). Species of Gymnusa Gravenhorst are uncommonly collected aleocharines that are associated with Sphagnum in wetlands and along streams.  In undisturbed fens and bogs, lightly pressing on water-logged vegetation will sometimes reveal specimens of this genus (Fig. 9.1.2). Tachyusa Erichson are characteristically shaped beetles found along the margins of lakes, ponds, wetlands, and streams; they are sometimes collected from beaver lodges (Fig. 9.1.3). Xenodusa Wasmann species live with colonies of Formica ants during the warmer months and overwinter with colonies of the ant genus Camponotus (Wheeler 1911) (Fig. 9.1.4). In ECAS, Aleocharinae are primarily predaceous on a wide variety of invertebrates, however some groups are strictly mycophagous (Ashe 1981) or parasitoids of cyclorraphous Diptera (Klimaszewski 1984).