32 Observations on Cynipidae. 



Male. Thorax and abdomen black, the latter 

 particularly shining ; legs light, dirty yellow, the coxae 

 and hind tibiae somewhat darker ; antennae dark, pale 

 at the base. 



Experimental breeding. After a sufficient number 

 of specimens have emerged from the galls, a certain 

 interval must be allowed to elapse to make sure that 

 the females are fecundated. When satisfied by the 

 examination of the 7'eceptaculum seminis of several 

 females that they have been fertilized, the experi- 

 mental breeding may proceed. On account of the 

 small size of the fly, it is better to continue the 

 experiments on the same tree on which the galls 

 grew. Care must be taken, however, to see that the 

 flies can reach the roots easily. In order to secure 

 this I planted several oak saplings in pots, with the 

 long woody root turned up again towards the surface, 

 so that the extremity protruded from the earth near 

 the trunk. Even if the extreme point were to die off, 

 lateral rootlets would form so near the surface that 

 the flies could easily reach them. On an oak arranged 

 in this manner I made an experiment on August i8, 

 1878. I was soon able to satisfy myself that several 

 of the flies, after exploring the surface of the rootlets 

 with their antennae, had finally pierced the root cortex 

 with their ovipositor. A subsequent examination of 

 the pricked spots revealed several eggs lying in the 

 cambium layer. 



The number of eggs laid at one spot varies greatly as 

 shown by the size and number of larva cells in the 

 later Aphilotrix radicis galls. I believe it frequently 



