FIELD CROP INSECTS 



243 



they moult five times at intervals of ten days to two weeks 

 and are full grown by midsummer. The adults of this spe- 

 cies are l inches long with a wing-expanse of 2 inches and 

 a bright yellowish-green color. The head and thorax are 

 olive-brown ; the fore wings are much the same color without 

 markings but with a brownish shade at the base; the hind 



FIG. 169. The differential locust (Melanoplus differentialis Thos.). 

 (After Riley.) 



wings are tinged with green; the hind thighs are bright yel- 

 low, with four black marks, and the hind shanks are yellow 

 with black spines and a ring of the same color near the base. 

 The adults at once attack whatever crops are available, 

 often finishing the destruction of those injured by them as 

 nymphs, but in a few days their appetites ssem to become 

 somewhat appeased and they 

 commence to mate and wander in 

 search of suitable places for laying 

 the eggs. Relatively few eggs are 

 laid in cultivated ground, the fa 

 vorite places being neglected fields 

 grown up in grass and weeds, the 

 edges of cultivated fields, private roadways, banks of ditches 

 and small streams, and pasture lands. It is doubtless due 

 to these egg-laying habits and the abundance of food on un- 

 cultivated land that this species always increases enormously 

 on land which has been flooded and then lies idle for a year 

 or two. Most of the eggs are laid in August and early Sep- 



FIG. 170. Egg-mass of the 

 differential locust enlarged. 



