108 FIRST BOOK OF ZOOLOGY. 



sharp, piercing sting, and with this organ the necessary hole 

 is made through which the egg is deposited. 



A caterpillar soon hatches from the egg thus deposited 

 by the ichneumon-fly, and feeds upon the fatty portions of 

 the body of the larva in which it has been so placed. But 

 this larva containing the ichneumon-caterpillar, meanwhile, 

 completes its growth and changes into a chrysalis, when the 

 inclosed ichneumon-larva devours the entire contents of the 

 chrysalis, and then changing into the pupa state soon emerges 

 as an ichneumon-fly, to go in quest of caterpillars, in which 

 to deposit its eggs. Thus it will often happen that a num- 

 ber of cocoons have been collected, from which ought to 

 appear a certain kind of a butterfly, for example, but from 

 many of them a brown ichneumon-fly will emerge, a sight 

 quite as startling, to one not familiar with insects, as if a 

 robin should be seen to hatch from a hen's-egg. 



If the pupils will collect from the fences a large number 

 of the chrysalides of the common yellow cabbage-butterfly, 

 and keep them in a box, with a piece of glass for a cover, 

 they will observe that while a butterfly comes from many, 

 from others, which have already changed to a lighter color, 

 little black flies will appear, crawling out of a hole in the 

 side of the chrysalis which had been made by some of the 

 imprisoned ichneumons. (See Fig. 104.) 



100. Nearly every species of insect is infested with one 

 or more species of ichneumons, which deposit their eggs 

 either within the pupae, larvae, or the eggs themselves. 



There are some species of ichneumons which deposit their 



