62, Observations on Cynipidae, 



Experimental breeding. In the year 1876 I made 

 experiments with this fly which showed me that it 

 pricked by preference the Httle adventitious buds on 

 the trunks of the older oak trees. My first attempts 

 were only made with a few flies in the open air, and 

 the results I then obtained proved later to be incorrect. 

 I repeated the experiments on a larger scale in 1878. 

 I had kept a large quantity of galls out of doors through 

 the winter, and in January the flies began to take flight. 

 I put them on a little oak indoors and observed that 

 after a few days they began to oviposit, choosing the 

 little adventitious buds that were on the stem. The 

 buds were pricked in the following manner. The fly 

 reared itself, directing its ovipositor to the point of the 

 bud, and bored down into it perpendicularly. The fly 

 is armed for this purpose with a tolerably straight and 

 strong ovipositor. Some time is required to complete 

 the act of ovipositing and the fly usually spends half an 

 hour in the pricking posture. In each bud, only one 

 ^^'g is laid. If a pricked bud is examined it will be 

 seen that the ^%% lies at the base of the bud-axis, in the 

 cambium layer which is continued into the bud, there- 

 fore it may be predicted with certainty that a bud-gall 

 will be the result. In my experiments thirty- four buds 

 were pricked between January 20 and January 26, 

 but it was not until the end of April that I was 

 able to observe the beginning of gall formation in any 

 of the buds. The points of the buds became dark blue 

 and soon the dainty velvety galls of SpatJiegaster Tas- 

 chenbergi became evident ; by the beginning of May 

 eleven galls developed on the tree. In the year 1879 



