THEIR RELATION TO EACH OTHER 



99 



that feed on grasshopper eggs, the adult beetles almost 

 without exception are devourers of plant tissue. Their 

 habit of coming to maturity at about the same time 

 brings clouds of them upon their food plants at once, 

 and gardens and certain truck crops suffer. It becomes 

 a question then, whether the insects are economically 

 more useful as destroyers of grasshoppers or more 

 destructive as feeders on crops. As to the species 

 feeding in the nests of bees, they are without question 

 economically injurious in all stages. 



Fig. 43. — Two common blister beetles: a. Macrobasis unicolor; b, Epicauta 

 pennsylvanica. 



But there can be no doubt either that in regions 

 where grasshoppers are very abundant, as they are 

 in the Rocky Mountain and some of the southwestern 

 areas of the United States, these blister beetles are a 

 most important check and one that has a large amount 

 of flexibility in effectiveness despite the fact that there 

 is only one annual brood. This is obtained by the 

 large number of eggs laid by the female, which in some 

 species runs into the thousands. The adults make no 

 attempt to place these near egg-pods, but only on 

 ground where such pods are likely to occur. It is up 

 to the young larva to find its own hotel accommoda- 

 tions or starve to death. When grasslioppers have been 

 scarce and pods are widely scattered, a very large per- 



