234 IIYMENOPTEKA. 



Between this cell and the exterior is a spongy sub- 

 stance. During the month of June many of the larvae 

 transform within the cell, and the winged insect makes 

 its exit through the little opening at h. These are 

 known as the spring gall-flies {Cynips quercus spongi- 

 fica^ O. S.), and consist of both males and females. 

 Others remain within the gall till about October, and 



Fig. 184. 



these are the fall gall-flies ( Cynips q. aciciilata, O. S.). 

 The later brood differs from the earlier by being en- 

 tirely composed of agamous females. Descriptions of 

 the Cynipidae of the North-x\merican oaks and their 

 galls are given by Baron Osten Sacken.^ 



1 Proc. Ent. Soc. Phil., Vols, I.-IL, 1861-64; Vol. IV., 1865. 



