THE, LIFE CYCLE 91 
a few easily perceived changes in its post-embryonic devel- 
opment, of an insect with an “incomplete metamorpho- 
sis.’ The eggs of grasshoppers are laid in little packets 
of several score half an inch below the surface of the 
ground. When the young grasshopper hatches from the 
egg it is of course very small, but it is plainly recognizable 
as a grasshopper. But in one important character it dif- 
fers from the adult, and that is in its lack of wings. The 
adult grasshopper has two pairs of wings; the just hatched 
young or larval grasshopper has no wings at all. The 
young grasshopper feeds voraciously and grows rapidly. 
Fie. 42.—Post-embryonic development (incomplete metamorphosis) of the Rocky 
Mountain locust (Melanoplus spretus). a, b,c, d,e,and jf, successive develop- 
mental stages from just hatched to adult individual._After EMERTON. 
In a few days it molts, or casts its outer skin (not the 
true skin, but a thin, firm covering or outer body wall com- 
posed of a substance called chitin, which is secreted by the 
cells of the true skin). In this second larval stage there 
can be seen the rudiments of four wings, in the condition 
of tiny wing pads on the back of the middle part of the 
body (the thorax). Soon the chitinous body covering is 
shed again, and after this molt the wing pads are mark- 
edly larger than before. Still another molt occurs, with 
another increase in size of the developing wings, and after 
a fifth and last molt the wings are fully developed, and 
