STRUCTURE AND DKVELOl'MEXT OF INSECTS. 9 



the surface of the earth, or in a silken cocoon spun by the 

 caterpillar, or merely attached to the food-plant })y a 



Fig. 2. — Complete Metamorphosis, The different stages of the 

 Corn Ear-worm {HeliotMs armiger Hlibn. \ a, eggs on corn- 

 silk; h, the first three larval stages; c, pupa from below; d, same 

 from above; e, adult moth — all enlarged; h, about twice natu- 

 ral size. (Original.) 



strand of silk or the cast larval skin. In many of the 

 Diptera, — the order including flies, mosquitoes, gnats, etc., 

 — however, the last larval skin is not shed, but hardens 

 and forms a case — called a puparium — within which the 

 pupal stage is passed. 



