102 INSECTS INJURtOCS TO STAPLE CROPS. 



ground, causing a slight enlargement at the point of 

 attack; but in the spring they usually stop at one of the 

 lower joints above the surface, in both instances becoming 

 fixed in the plant and weakening it by absorbing its sap 

 and tissues. 



Fig. 61. — The Hessian Fly and its various stages of development. 

 n, an iigg; b, larva or worm; c, flaxseed; d, pupa; e, adult, lay- 

 ing eggs; /, female; g, male; Ji, stalk of wheat showing attack; 

 i, natural enemy or parasite— all enlarged except wheat-stem 

 and fig. e. (After Riley, Burgess, and Trouvelot, from U. S. 

 Dept. Agr.). 



This difference in method of attack results in a corre- 

 sponding effect on the plant. The first indication of the 

 work of the maggots in the fall is the tendenc}^ of the 

 plants to stool out; the dark color of the leaves, which are 

 sopiewhat broader, and the absence of the central stems 



