Spathegaster baccarum. 17 



probable that most of the females of the brood have 

 been fertilized, and breeding experiments may be 

 proceeded with. 



The female flies are then placed on oak saplings, care 

 being taken that the leaves are tender and in actual 

 growth, as it is only in that condition that they can be 

 pricked. Unless leaves in this state can be provided, 

 no results need be expected. 



I made my first observations on ovipositing in Spathe- 

 gaster baccarum in the open air. In the year 1875, 

 from June 18 to 21, I watched many of the females 

 creeping about on the tender oak leaves and pricking 

 them on the under surface. Having marked the pricked 

 leaves by tying a thread around the leaf-stalk, I waited 

 for the development of the galls. In about three weeks 

 the beginning of gall formation was observable, and the 

 galls could soon be recognized as those of Neuroterus 

 lenticularis. 



In June, 1876, I placed flies, reared by myself, on an 

 oak sapling and repeated this same experiment under 

 more exact control. Two leaves were pricked, and at 

 the end of twenty days I recognized the first beginning 

 of gall formation, and the galls again proved to be 

 those of Neuroterus lenticularis. 



Now the mystery was completely solved, and I had 

 discovered what became of the eggs laid in the buds by 

 Neuroterus lenticularis, and why the galls appearing in 

 July are found in such numbers on a single leaf. 



[The currant gall is found in May on Quercus pedunculata, 

 Q. sessiliflora, and Q. pubescens. 



Inquilines. Synergus albipes in May and June. S. facialis and 

 S. radiatHS in June. S. apicalis, S. ruficornis, 5. thaumacera. 



C 



