:3()2 



BEES AND WASPS 



color, and if observed tliese may be allowed to remain in 

 the fields with the expectation of the parasite serving a 

 good purpose for a later generation. If possible it is well 

 to assist them somewhat by putting the pupse under screens 

 which will permit the escape of the parasites, without 

 allowing the escape of butterflies which might issue from 

 healthy pupte. 



While most of these species are parasitic, there are a few 

 which are plant feeders, and notable among these is the 



-■i 



Fig. 245. — Bits of hardened straw remaining with the grain after 

 thrashing. (After Webster, Div. Ent.. U. S. Dept. Ag.) 



wheat joint worm {Isosonia tritici), which is the cause of a 

 great deal of damage to wheat in many parts of the country. 

 The presence of the joint worm is evidenced by the forma- 

 tion of woody places in the stem, within which the worm 

 is found and the effect of its injury is to cause the stems to 

 become weakened so that freciuently the grain will be broken 

 down, especially if there are severe winds. The insects pupate 

 within the stems and remain in the pupal stage all winter. 

 This accounts for their frequently being fountl in chaff" or 



