1896.] 2U5 



the wing8, where it matches in tint the browner fringes of the ahilae ; prothoracic 

 air-nipples hkewise of the lighter brownish hue, contrasting with the adjacent white 

 hair. Abdomen dorsally with pubescence concolorous with that of the neighbouring 

 part of the thorax, but ventrally, from certain standpoints, with blackish pubescence. 

 The dark fascia across the wing, like a curved, inverted, ill-formed y, encloses the 

 white spot at the end of the axillar nervure ; its inner border in this sex crosses the 

 radial branches shortly beyond the bifurcation and touches the axil of the pobrachial 

 fork. Legs dull black or brownish-black, with glossy white scales at the apical 

 margins of the tibiae and of the tarsal joints ; in addition, from certain standpoints, 

 when shifted about, an impure whitish gloss overspreads the dorsa of the tarsi from 

 the tip of the 2nd joint to the 5th (leaving in certain positions the bases of most of 

 the joints dark), and is extended over the soles of the hinder tarsi, while on the 

 fore-leg it is continued in front to the knee, and frosts the tibial fringes. When the 

 fly moves about among the herbage of watery ditches, the play of light on these 

 parts and on the head and thoi'ax, and more especially upon the bristling hair of the 

 wings, produces a fitful glow, like opal or phosphorous, that attracts attention. 



$ . Pubescence of head, thorax and dorsum, and from certain standpoints the 

 bristling hair of the wings, whitish-grey, shifting to a light grey and impure whitish 

 when turned about ; ventral pubescence dark grey. Scales and hair of the antennae 

 similar in tint to the other hair of the head ; flagellum from certain positions light 

 sepia-brown. Wings greyer than in the male ; the dark fascia is broadest on the 

 radial branches and cubitus, and in this sex its inner border crosses both of the 

 forked nervures considerably beyond their bifurcations. The tibiae and tarsal joints 

 have white scales at their apical borders as in the male ; but the whitish gloss is 

 limited to the apical joint of the anterior tarsus, and can hardly be induced to spread 

 farther than the dorsa of the last three or four joints in the hinder tarsi, the soles 

 in most positions remaining lustreless. Season, May to July, and September. 



Haliday's application of Meigen's name canescens (Joe. cit.) to the 

 present species could not be adopted, because the markings of the tarsi 

 are unsuitable. This has already been noticed under Pericoma No. 9, 

 supra, p. 73. Walker had several specimens variously labelled in his 

 cabinet ; but in every instance they were associated with some of other 

 species, in a similar manner to those specified under Pericoma No. 16, 

 supra, p. 203. P. notalilis was not included by Mr. Verrall in his 

 tiist of British Diptera (1888) ; but the species was known to him, 

 being well represented in his collection by specimens of earlier date 

 from the following localities : — Lyndhurst, Hants, June, 1869 ; Fritton, 

 Norfolk, June, 1881 ; Newmarket, Cambridgeshire, September, 1884 ; 

 Burwell, Cambs., May, 1886. He subsequently met with it at Slapton, 

 Devon, September, 1889. 



It would be well to verify the species of the small insect from 

 Chesil, in the Isle of Portland, cited in the original description of P. 

 notahilis, and classed as such chiefly on account of the structure of 

 the antennje and other characters that are here noted as of Sub- 



