JUL i 13SB 



June, 1S98. 121 



Kord, France, p. 168 (1824) ; Haliday, Ent. Mag., i, 148 [list] (1833) ; Macq., 

 Hist. Nat. Ins. Dipt. [Suites a Buffon], i, 164 (1834) ; Ferris, Ann. d. So. Nat. 

 France (2), xiii, 346—8, pi. vi, fig. B [pupa, not larv.] (1840) ; Eossi, Dipt. Aust., 

 p. 6 (1848) ; Curt., Journ. Eoy. Agricult. Soc, x, part i [No. xxiii, July], p. 103, 

 pi. V, 47—50 [pupa] (1849) ; Zetterstedt, Dipt. Scand., ix, 3706 (1850). 



(? . Antennae usually 14-jointed, and, when fully developed, reaching nearly to 

 the middle of the wing, but often stunted ; in the former condition the verticils of 

 long hair of the flagelium compose a smooth moniliform series of subspherical 

 cupules, the open end of one cupule fitting the base of the next. Hair of head and 

 body impure white, or whitey-brown anteriorly, but light brown from certain stand- 

 points posteriorly. Wings in the living fly blueish ash-grey, or dove colour, the blue 

 and reddish iridescence of the membrane mingling with the colour of the hair, 

 which changes with posture from white to whitey-brown ; wing-margin in trans- 

 mitted light opaque, but otherwise concolorous with the disc ; fringes shifting from 

 satiny-white to whitey-brown or greyish when turned about, the costal fringe in 

 suitable positions becoming dark, independently of the posterior fringe. At the 

 base of the wing, viewed from in front, the hair of the tegulae appears white or 

 wliitey-brown, but the " humeral tuft " arising from the thickened portion of the 

 costa opposite the mediastinal (this thickening is sometimes piceous in dried speci- 

 mens), and overlying the costal fringe thereabouts, although matching with the 

 fringe from certain standpoints, readily shifts to dark brown or grey, and even to 

 blackish towards the roots of the hairs. Bifurcation of the radius perhaps always 

 interior to the end of the axillar nervure. Grenital segment often inverted, probably 

 by torsion during copulation (an accident that frequently occurs in Pericoma ex- 

 quisita) ; basal joint in the superior appendages sub-cylindrical, subequal in length 

 to the forceps-basis ; apical joint subulate, very slightly curved. Inferior append- 

 ages neatly forficulate, at first very shortly convergent from their insertions and 

 thereabouts rounded off beneath, then for a short space subparallel with each other, 

 slightly arcuate upwards throughout, and finally gently incurved towards their tips ; 

 each of them subulate with the extreme point suddenly acute, nude dorsally, but 

 elsewhere beset with rather long, dense, spreading hair ; tenaculum exactly apical, 

 slightly foreshortened by perspective in the cited figure ; from other standpoints 

 more slender and subspatulate, or narrowly ob-triangular and rounded off at the 

 obtuse angle. Indumentum of legs glossed with dull satiny-white ; the appressed 

 scales narrowly linear. 



? . In dried specimens of this species the legs ai-e usually rather darker, and 

 the wing-neuration a little more distinct than in Ps. albipennis, but tlie body is not 

 always more opaque ; in fact, the specific identity of Psychodce of this sex, unac- 

 companied by males from the same localities, cannot always be guessed at with 

 certainty. The name nervosa, Schrank, was probably applied to worn specimens of 

 the female. 



The larvae feed upon all sorts o£ decaying vegetable substances, 

 and the geographical ditipersion of this species is doubtless extensive. 

 The flies abound in the British Islands, Haliday being the authority 

 for Ireland, and Mr. J. J. F. X. King's collection for Scotland (Loch 

 Marec, 1»90, 4 J, 1 $). A. Maltese ? specimen in the British 



L 



