50 



INSECTS INJURIOUS TO STAPLE CHOI'S. 



often be found which niiiy be distinguished by a compari- 

 son of the caudal segment with the illustrations (Figs. 27 

 and 28). The adult beetles arc mostly about one-half to 

 three-fourths of an inch long, decidedly flattened, of a 

 dark brown coJor, with short heads and shield-shaped 

 thoraxes, as in Fig. 2G. 



Life-history. — Land wliich has been in grass for several 

 years is their native breeding-ground, and here the eggs 



Fig. 26. — A, Beetle of Wheat Wirew^^rm; B, Dmsterius elegnns, 

 both enlarged about 4 diameters. (After Forbes.) 



are deposited. Much concerning the life-histories of these 

 important pests is still unknown, but it seems safe to assert 

 that the larvae require from three to five years to become 

 full-grown. Thus the second year after grass land has 

 been planted in grain is that in which the worst injury 

 occurs, and this is especially true with corn, wliich covers 

 the ground less completely than do the smaller grains, 

 The larvffi become full-grown in midsummer, form a small 

 earthen cell, and there transform to the pup^e. Three or 

 four weeks later the adult beetles shed the pupal skin, but 

 only a few of them make their way to the surface during 



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