THE LARVA 25 



When the fatty 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 bulk shows often no very appreciable decrease 

 in size. When the larvae 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 time 

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

 chrysalis before its fate is sealed. In this latter case, a number of 

 flies, having undergone their final transformation within the 



FIG. 17. AN ICHNEUMON FLY FIG. 18. -ANOTHER ICHNEU- 



(Cryptus Migrator). MON FLY (Pimpla^ Insti- 



gator). 



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 butterfly or moth should 

 have appeared. 



Caterpillars have also their nocturnal enemies and devourers, 

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

 eating mammals. 



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 large species, that is not very densely covered with 

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



