196 NEMATUS ISCHNOCERUS. 



The larva lives solitarily in galls on Salix purpurea 

 and 8. laurina. The galls are usually in pairs on a 

 leaf, placed opposite to, and almost touching, each 

 other. They project to some extent above, but not at 

 all from the lower side of the leaf. In form they are 

 roundish or oval, sometimes long and narrow, the 

 sides having round projecting rings ; the colour on the 

 upper surface is dark purple, reddish-pink, or in some 

 rare instances dark green ; beneath it is always pale 

 green. When very young they are of a uniform green 

 colour. 



In its habits the larva agrees in the main with that 

 of N. gallicola, but it does not make a hole for the ex- 

 pulsion of the frass until a later period than that insect. 

 It devours the gall very closely, and by the time it has 

 become full-fed its habitation is reduced to a bladder, 

 all but the skin having been eaten. I have found 

 galls which had every appearance of being composed 

 of two galls amalgamated, but only one larva could 

 be seen inside. It is also interesting to notice that 

 often on the same leaf two galls may be found, in 

 one of which the larva will be far more advanced in 

 its development than the other. In one instance a larva 

 was still in the egg, whilst the other was in the com- 

 mencement of the second moult. 



When full-fed the larva has the head of a white 

 colour, more or less marked with fuscous above ; the 

 eyes are placed in black spots. Mouth brown. The 

 legs are greenish-white ; over each of the thoracic 

 pairs is a black band ; the claws are black. When 

 the creature is feeding the dorsal vessel is green, the 

 rest of the body being of a dirty-white colour, slightly 

 tinged with green, and covered with a few scattered 

 hairs. The body tapers towards the end, and the seg- 

 ments project much at the sides ; the abdominal legs 

 are invisible above and to a certain extent laterally by 

 being hid by the overhanging folds of the body. The 

 head varies in the amount of fuscous with which it is 

 marked. 



