Chamaepsila strigata (Collin, 1959)

Collin, 1959: Psila strigata sp. n.

Upper half of occiput darkened, this darkening being continued on to the ocellar triangle of frons, and rather less extensively and narrowly on upper part of frontal orbits. The two basal joints, and the extreme base of third joint, of antennae, yellow, rest of third joint very black. Arista whitish and distinctly pubescent, though less so than in pectoralis. Chaetotaxy as in species of this group, with two orbitals and three verticals on each side. Palpi yellow but slightly brownish at tip. Thorax black with humeri at least partly yellow (usually somewhat darkened on upper surface). Pleurae yellow except for a conspicuous dark upper band beginning narrowly on upper margin of mesopleurae, but widening out behind until it joins the dark postnotum below scutellum. Lower part of pleurae including sternopleurae entirely yellow. Two pairs of dorsocentral bristles placed rather more distant from each other than in humeralis, more so than the distance between a pair, and the short pale hairs on thoracic disc less numerous, with only about four rows between the front pair of dorsocentrals; in both these respects more resembling pectoralis. Abdomen shining black. Male hypopygium small, of a similar type to that of humeralis. Legs pale yellow. Wings clear, veins yellowish. Halteres white. Length about 3 mm.

In addition to the differences from humeralis mentioned above,the pleurae of humeralis (of which numerous specimens from Scotland have been examined) are always more extensively darkened, and sternopleurae almost entirely darkened, thorax at sides of disc more extensively yellow, third antennal joint on outer side entirely pale yellowish-brown instead of black, and palpi entirely yellow. P. pectoralis is less well known to me, but the arista has longer
pubescence than in the new species, and the pleurae are nowhere darkened. Hennig, to whom both pectoralis and humeralis appear to have been well known, has indicated in Lindner's "Die Fliegen, Psilidae" that he considered the pleural colour characters to be constant in both species.