164 



LOCUSTS, BUTTERFLIES, BEES, WASPS 



become larger and larger until after the last molt they appear 

 fully developed (Fig. 102). Such a development — in 

 which the egg hatches into a form resembhng the adult — 

 is known as a direct development, and insects having a 



Fig. 102. — Nymphs of a locust : A, first stage ; B, second stage ; C, third 

 stage; D, fourth stage; E, fifth stage; F, final stage. After Emerton. 



direct development are said to have an incomplete meta- 

 morphosis. 



Economic importance of the locusts. — Since locusts 

 persistently feed upon grasses, grains, and forage crops, 

 they are of considerable economic importance, although the 

 Carolina locust does not cause so much injury as some other 

 species. The Rocky Mountain locust, that in past years 



