i6 Observations on Cynipidae. 



sappy consistence ; the gall grows through the leaf, 

 its larger segment projecting from the lower surface 

 of the leaf. This gall not only occurs on the leaves 

 but is found also on the peduncles of the male 

 catkin, and is then smaller and of a pale reddish 

 colour. (Fig. i^) 



Fly. Size, 3-5 mm. ; of a black colour ; thorax dull, 

 slightly rough ; legs and coxae yellow, as also the basal 

 segments of the antennae. Abdomen distinctly pedun- 

 culate. The male has fifteen, the female fourteen joints 

 to the antennae. The wings are long, broader towards 

 the tip, and longer than the body. 



Rearing the Fly. The fly emerges from the begin- 

 ning to the middle of June. Owing to the sappy 

 nature of the galls it is not wise to collect them too long 

 before the flight time of the fly, otherwise it is difficult 

 to prevent the galls from shrivelling and drying. In 

 order to hatch the flies satisfactorily it is absolutely 

 essential to keep the galls fresh : it is scarcely possible 

 to do this for longer than eight days in closed tin or 

 glass vessels. Since these flies occur in both sexes it 

 is necessary to see that they copulate before ovipositing. 

 I have been in the habit of spreading the galls out on 

 damp sand as I collected them, and placing over them 

 a gauze covering. The males are usually the first to 

 appear, and as soon as the females emerge fecundation 

 takes place, but generally too rapidly for this to be 

 actually observed. To demonstrate that it has occurred 

 it is necessary to prepare the receptacula seminis of some 

 of the females for microscopical examination. If these 

 are found filled with spermatozoa it may be taken as 



