298 The Scottish Naturalist. 



not seem to be such voracious feeders. Neither do they leave 

 the galls until they have become full fed ; and I have always 

 noticed that the exit-hole is invariably made too small, so that 

 they have some difficulty in escaping. They walk very fast when 

 outside the galls. The coffee-brown cocoon is longish, scarcely 

 cylindrical, and the silk of which it is composed is very thin. 

 In the breeding-jar they were spun in the earth in masses, one 

 against the other. Some individuals that were confined in a 

 white pill-box spun perfectly white cocoons, while others bored 

 into the cork of the bottle in which they were kept, and formed 

 them there, — the hole hollowed out being exactly of the size of 

 the cocoon. 



The flies make their appearance from April to July, and the 

 galls are found from June to October. I am certain that there 

 is not more than one brood in a year, notwithstanding the fact 

 that I have reared the imagos in July from larvae collected in 

 June. At the Clyde Iron Works, on the banks of the Clyde 

 above Glasgow, the galls are found in thousands, and Mr. 

 Traill has sent me them from the vicinity of Aberdeen. 



Imago. Antennae a little longer than the abdomen, entirely 

 black, or with the apical joints underneath brownish ; the third 

 and fourth joints equal, the remainder minutely decreasing in 

 length. Head black, shining, in certain lights appearing as if 

 covered with whitish pubescence ; ocelli black ; the eyes in 

 some specimens are encircled with brown in the rear. Mouth 

 testaceous white, scarcely pubescent ; mandibles black ; palpi 

 obscure white, with the bases black. Thorax black, shining ; 

 pronotum lined with white, broadly so at the tegulae, which are 

 of the same colour. Breast black, shining. Cenchri obscure 

 white, often not visible. Abdomen short, thick, and above 

 1 >lack, with only a very minute point at the apex testaceous ; 

 beneath black, with the apical four or five segments obscure 

 testaceous in the centre ; apex angustate, pilose. Feet reddish- 

 yellow, the red predominating; coxae and trochanters with a 

 decided yellow tinge ; tibiae covered with white down ; anterior 

 tarsi, with the joints from the apex of the first, brownish ; pos- 

 terior pair totally brownish-black, as well as the apex of the 

 tibiae and the calcari. Wings hyaline, but faintly dark through- 

 out, iridescent ; costa and nervures pale at the base ; stigma 

 totally black or fuscous-black, or with only a very small point 

 at the base fuscous. The nerve of the second sub-marginal 

 cell is usually very faint ; the second sub-marginal cell is small 



