218 HYMENOPTEKA . 



honey-yellow costa, and a dusky stigma, edged with honey- 

 yellow. The male differs a little in having black eoxse. Mr. 

 Walsh states that the larva is a pale grass-green worm, half 

 an inch long, with a black head, which becomes green after 

 the last moult, but with a lateral brown stripe meeting with 

 the opposite one on the top of the head, where it is more or 

 less confluent ; and a central brown-black spot on its face. 

 It appears the last of June and early in July, and a second 

 brood in August. They spin their cocoons on the bushes on 

 which they feed, and the fly appears in two or three weeks, the 

 specimens reared by him flying on the 26th of August. P. 

 sycoplianta Walsh is an " inquiline," or guest gall-saw-fry, 

 inhabiting a Cecidomyian gall on a willow. 



The genus Euura comprises several gall-making species. ' It 

 differs from the preceding genus in the second, instead of the 

 first, submarginal cell having two recurrent venules. Mr. 

 Walsh has raised E. orbitalis Norton (E. genuina Walsh) from 

 galls found on Salix humilis. This gall is a bud which is 

 found enlarged two or three times its natural size, before it 

 unfolds in spring. The larva is twenty-footed, is from .13 to 

 .19 of an inch long, of a greenish white color, and the 

 head is dusky. It bores out of its gall in autumn, descending 

 an inch into the ground, where it spins a thin, silken, whitish 

 cocoon. The gall of E. salicis-ovum Walsh is found on Salix 

 cordata. The female is shining yellow, while the ground color 

 of the male is greenish white. The gall of this species is an 

 oval roundish, sessile, one-chambered, green or brownish swell- 

 ing, .30 to .50 of an inch long, placed lengthwise on the side of 

 small twigs. The larva is pale yellowish, and the fly appears 

 in April. The fly is, according to Walsh, " absolutely undistin- 

 guishable by any reliable character from the guest gall-saw-fry, 

 Euura perturbans Walsh," which inhabits dipterous galls made 

 \)j Cecidomyian flies on the willow and grape (Walsh) . If these 

 two " species" do not differ from each other, either in the larva 

 or adult state, "by any reliable characters," then one must 

 question whether the variation in habits is sufficient to separate 

 them as species, and whether E. salicis-ovum does not, some- 

 times, instead of forming a new gall, lay its eggs in a gall ready- 

 made by a dipterous gall-fly. We have seen that Odyiierus 



