NEMATUS GALLIOOLA. 203 



tegulae, and legs, whitish-yellow ; the greater part of the coxae, and a 

 more or less longish line on the femora (which have often a reddish 

 tinge), black ; the base of posterior tibia3 and the tarsi fuscous. An- 

 tennas a little longer than the abdomen, the apical joints often brownish 

 beneath; pentagonal area and sutures on front obsolete, sutures on 

 vertex short ; antennal fovea large, deep. Wings hyaline, costa pale, 

 stigma a little longer than broad, almost quadrate ; second transverse 

 nervure often nearly interstitial ; upper middle cellule in hind wings 

 smaller than lower. 



The $ has the antennae longer, thicker, and more pilose, and the 

 flagellum brownish ; the stigma is almost wholly fuscous ; the wings are 

 not so clearly hyaline, and the femora bear more black. 



Length If 2 lines. 



A smaller species than N. salicis-cinerece. The legs 

 are whitish, not luteous as in the latter; the frontal 

 area and sutures are obsolete, not distinct as in salicis- 

 cinerece, and the stigma is more largely white, the fus- 

 cous predominating in the stigma of salicis-cinerece. 



The is extremely rare, and the species is certainly 

 parthenogenetic, Mr. Fletcher and myself having got 

 virgin females to lay fertile eggs, but neither of us 

 succeeded in rearing any flies from them. Dr. Adler, 

 however, has been more successful, for he managed to 

 get some virgin females to oviposit in June, reared the 

 flies (females) from the galls in July, these again laying 

 eggs which yielded larvae that spun up in October 

 (Z. wiss. Zool., xxxv, 208). 



The larva lives solitarily in galls on various willows, 

 being most abundant on Salixfragilis. The galls are 

 bean-shaped, the skin covered with small irregular 

 projections and hairless. In length they vary from a 

 quarter to half an inch, one-eighth to a quarter of an 

 inch in breadth, and about the same in depth, are 

 always placed on the edges of the leaf, and project in 

 about equal proportions through both sides. When 

 young the colour is light green, but as they get older 

 this gives place to a deep red above and a paler red or 

 light green beneath. The number on a single leaf 

 varies from one to thirteen, which latter is the largest 

 number I have noticed. On Salix alba they are usually 

 pale green, seldom light red, and hairy on the under- 

 side. 



