HYMENOPTERA 



899 



The wheat-sawfly-borer, Cephus pygmcsus. — The larvas of this 

 species bore in the stems of wheat, a single larva in a stem, dwarfing 

 and stunting the growth of the plant. As the grain becomes ripe the 

 larva works its way toward the ground; and at the time of harvest 

 the greater number of them have penetrated the root. Here, in the 

 lowest part of the cavity of the straw, they make preparations for 

 passing the winter, and even for their escape from the straw, as adults, 

 the following year. This is done by cutting the straw circularly on 

 the inside, nearly severing it a short distance from the ground, so 

 that a strong wind will cause it to break off at this point. After the 

 circular cut has been made, the larva fills the cavity of the straw just 

 below it for a short distance with a plug of borings. Between this 



Fig. 1 139. — ^Wings of Cephus pygmceus. 

 Gillivray.) 



The cells are lettered. (From Mac- 



plug and the lower end of the cavity, the wall of the cavity is lined 

 with silk forming a cocoon within which the larva passes the winter 

 and changes to a pupa in March or April. The adult insects emerge 

 early in May. 



The currant-stem girdler, Janus Integer. — The larva of this species 

 bores in the upper portion of the canes of currant. Its presence is 

 indicated by the wilting and drooping, in late spring, of the new 

 growth at the tip of the infested cane. This is due to the fact that 

 the parent sawfiy after depositing her egg in the cane moves up a 

 short distance above where the egg is deposited and with her ovipositor 

 girdles the cane, sometimes nearly severing it. This killing of the 

 tip, and thus checking the growth of the cane, seems to be necessary 

 for the development of the egg and larva. The larva bores in the 

 pith of the cane. In the fall it eats a hole through the woody wall 

 of the cane to the outer bark, thus making provision for the escape 

 of the adult, and then spins a cocoon in which it hibernates. The 



