THE LARVA 



25 



When the fattj' substance is nearly all gone, they eat their way 

 into the more important structures, of course steadily growing all 

 the time ; and so, even though the body of the caterpillar is rapidly 

 diminishing, the total bulli shows often no very appreciable decrease 

 in size. When the larvic of the flies are fully fed, they either 

 change to the pupa within the carcase of their host, or eat their 

 way out of its body and construct for themselves a cocoon in which 

 to undergo the transformation. 



As for the caterpillar itself, it sometimes dies before the tune 

 for its metamorphosis has arrived ; but it often changes to the 

 chrj'salis before its fate is sealed. In this latter case, a number of 

 flies, having undergone their final transformation within the 



o% ro 



Fig. 17. — An Ichneumon Flt 



{Cnjj)tus Migrator). 



Fig. 18. — Another Ichneu- 

 mon Fly (Pimjjla Jjisti- 

 fjator). 



chrysalis shell (there being but little else than shell remaining 

 of the victim's body), break forth from the remains of the carcase 

 somewhere about the time at which the buttertly or moth should 

 have appeared. 



Caterpillars have also their noctiu'nal enemies and devourers, 

 among which may be mentioned frogs, toads, newts, and insect- 

 eatmg mainmals. 



We must now learn something of the structure of caterpillars ; 

 and then become acquainted with their habits, and the change to 

 the chrysalis or pupa. 



Take a caterpillar from your garden, preferably a full-grown 

 one of a rather lai-ge species, that is not very densely covered with 

 hair, and examine it carefully as we note the main points in its 



