Probably the most common British species of Passaloecus, at least in the south.

In the older literature this species has been placed in the genus Notozus, where it was known as scutellaris or constrictus. Identification keys and general biology are given in Morgan (1984) and Kunz (1994).

Identification keys and general biology are given in Krombein (1967), Morgan (1984) and Kunz (1994). Great care must be taken when distinguishing this species from O. puncticollis.

An all-black species with bifasciate wings. Identification is not too difficult using Day (1988), but it should be noted that the captions to figures 40 and 42 are transposed. The generic name refers to the tufts of forward-pointing bristles on the maxilla of the female; these are used to pack the nest entrance with old spider silk.

A small, black sphecid wasp, formerly placed within the genus Psen. It is one of ten species currently placed within the genus Mimumesa to be found in Europe, and is probably the most widespread of those species.

A small, ground-nesting, red and black solitary wasp. The nomenclature of this species has been the subject of some confusion. Identification keys are given in Yeo & Corbet (1995) (as Psen bicolor); Lomholt (1984) (as Mimesa rufa), and Richards (1980) (as Psen bicolor). Prior to the publication of a paper by Spooner in 1948 the species was referred to as Psen equestris, so care is needed when citing older records of this wasp.

First found in Britain in 1978 by M. Edwards. An important paper on this species is that by Else (1997). See also Dicker (1982). A key to European species groups of the genus Passaloecus is given by Merisuo (1974).

Passaloecus species are small to very small, elongate, black wasps which nest particularly in beetle borings in posts and other cavities, and prey on aphids. The biology of this species is described by Merisuo (1973), and keys to the European species groups of the genus Passaloecus are in Merisuo (1974).

One of three large species of Priocnemis with plentiful erect hair on the face and propodeum (subgenus Umbripennis). P. perturbator is often found at the flowers of Wood spurge, Euphorbia amygdaloides, in woodlands during May. Identification is given in Day (1988). Many early records for this species may be confused with those for its close relative P. susterai Haupt.