Osoriinae Erichson 1839
  Figure 1.17.1 Renardia nigrella LeConte, dorsal abdomen. 1.17.2 Thoracophorus costalis Erichson, dorsal abdomen. 1.17.3 Eleusis pallida LeConte, head and pronotum. 9.8.1 T. costalis, found under wood in leaf litter.    

Osoriines are characterized by a parallel-sided abdomen that lacks sutures on the dorsal surface (Fig. 1.17.1). The abdomen can either be flattened and with a single lateral suture (Fig. 1.17.1), or cylindrical and formed of fused tergites and sternites (Fig. 1.17.2). The only staphylinids with a similar abdomen are species of Palaminus Erichson (Paederinae), which do not have the last maxillary palpomere smaller than the previous one (as in Fig. 1.17.3) and some Stenus Latreille (Steninae), which have large convex eyes that occupy most of the lateral head outline.


The Osoriinae is a widespread subfamily in North America but it remains taxonomically and biologically poorly known. The species inhabiting ECAS are generally found under bark, in leaf litter and in ant nests in decaying wood.  Osoriinae are very poorly represented in collections of ECAS insects, possibly because they are really rare, or possibly because they are merely secretive; adults of some Renardia Motschulsky are winter-active under bark.  The most common species in ECAS, Thoracophorus costalis Erichson (Fig. 9.8.1), is often found under bark (especially of large beech logs), but sometimes occurs in leaf litter and on conk fungi.  Motter (1898) found a large number (up to 160 individuals) of Eleusis pallida LeConte adults and larvae in human graves in sandy soil, although this species too is normally found under bark. This strange report may indicate subterranean larval and/or pupal stages. Osoriines are saprophagous or mycophagous as far as known.