122 [June, 



31. Pericoma fusca, Macquart. 



^.—Psijchodafusca, Macq., Ins. Dipt. Nord France [110 (1824)], 

 or 167 (1S2G) ; id., Hist. Nat. Ins. Dipt. {Suites a Buff on), i, 164 

 (1834).— P6-. + tristis, Z^tt., Dipt. Scand., xii, 4887 (1855), [«ec* Meig.]. 

 — Pericoma + tristis, Schiner, Fn. Aust. Dipt., ii, 634 (1864), \nec* 

 V. d. Wulp]. — P. fusca, ! Etn., ante, 2nd ser , vol. iv, 32, step 5, and 

 vol. V, pi. iv, P. 31 ( J «fc ? , details). 



? .—Psychoda calceata, Meig., Sjst. Eeschr., vi, 272 (1830) ; Zet., 

 Dipt. Scand., ix, 3706 (1850). — Pericoma calceata, Walli., Ins. Brit. 

 Dipt., iii, 260 (1856) ; Schiner, Fn. Aust. Dipt., ii, 634 (1864) ; V. d. 

 Wulp, Dipt. Neerl, i, 318 (1877). 



(? . Base of wing, interior to the parting of the bristling hair from the smoother 

 hair, darkened by the indumentum of the under-side, and so contrasted with the 

 further portion in depth of tint, mucli as if the hair had been tliiiined out with a 

 squeeze. The dark spots contiguous with the parting contrast in this sex only very 

 faintly with the other bristling liair, yet form an abbreviated broken transverse 

 band, narrowed posteriorly and touching the axil of the radial fork, but well beyond 

 that of the pobrachial nervure. Axillar nervure in tliis sex without bristling hair, 

 tabescent and slightly undulate, with the rising arch exterior to the hollow : anal 

 nervure arched a little more strongly from the cross vein to the margin and gently 

 sinuate across the curvature ; both nervures clad with long, prostrate, tristichous 

 hair, the middle rank overlying the nervure, shorter than the others that are spread 

 outwards from it and applied to the membrane. Subcosta for some distance beside 

 the stem of the radius, in high relief, a narrow fold in the membi-ane intervening 

 between them, as usual. Fringe of the alula dense and remarkably long (the 

 longest hairs would reach from the radial bifurcation to the end of the axillar 

 nervure), constituting a well-furnished fascicle or tuft of brown hair, which appears 

 to be laid along the axillar area (the fringe of the margin thereabouts being deflected) 

 and is a little longer than that area. Hair of the humeral tuft and commencement 

 of the costal fringe, long, very dense, and spreading. 



At the base of the wing, beneath the region of bristling hair, all the nervures 

 are squaniate : from the i-adius to the postical nervure the scales are of moderate 

 length, linear, at first subobtuse, then acuminate, distichous, divergent, and partly 

 subsecvuid, partly appressed to the membrane ; farther out the scales are succeeded 

 for a short space by flattened hair and this by ordinary hair likewise distichous. 

 On about the first half of the subcosta the scales are of similar form, but very dense, 



.ind that the wing there figured is stated to be that of a Pericoma ; while to illustrate the two 

 genera here under consideration, Westwood, in pi. xxvi, figures certain details of Psychoda 

 tex2^iinctalo, Curt., and the head and thorax "of a Pericoma ;after Curtis;." 



In Walker's cabinet, under the label Psychoda paluxlris, are three rows of four specimens 

 each, composed altogether of six specimens of U lamina fulipinoKa, four of Pericoma nubila, aTid 

 two of P. iiolabilis—i\ 6 at the beginning and a 5 at the end of the lowest row. So perhaps the 

 citation of auriridaia under (8) paLtistris in his book may have been Walker's doing, on the sup- 

 position that the 6 n'ltabilis, because of the air-nipples, must have been Haliday's insect, 

 regardless of the form of the wing, and without troubling to compare the specimen before him 

 with the description of palustris. 



* Ps. Iriftis, Jleigen, Syst. Beschr., vi, 272 (]830'i, measuring only 1 lin., is likely to have been 

 one of the minor species closely resembling P. snleata t21). P. t trittis, V. d. Wulp, Dipt. Neerl., 

 i, .319, on accoiuit of the position of the central cross vein and the length of the basal cell, is 

 scheduled, loe. cit., with P. nubila (6). 



