496 



AN INTRODUCTION TO ENTOMOLOGY 



The wonderful instinct by which the triunguHns of these bhster- 

 beetles find their way to the nests of soHtary bees has not yet reached 

 perfection ; for many of them attach themselves to flies, wasps, honey- 

 bees, and other flower-visiting insects, and merely gain useless trans- 

 portation thereby. 



The life-history of Epicauta vittdta, which was worked out by 

 Mr. C. V. Riley ('77), wnll serve to illustrate the hypermetamorphosis 

 of blister-beetles. The adult beetle is yellowish or reddish above, 

 with the head and prothorax marked with black and with two black 

 stripes on each wing-cover (Fig. 587, F). It feeds on the leaves of 

 potato, and is sometimes a serious pest. The female lays her eggs in 



Fig. 587. — Hypermetamorphosis of Epicauta vittata. (From Sharp, after Riley.) 



the ground in loose, irregular masses of about 130 each; several such 

 masses are laid by a single female. vShe prefers for purposes of ovi- 

 position the very same warm, sunny locations chosen by the locusts 

 for laying their eggs. The triungulins that hatch from the blister- 

 beetle eggs (Fig. 587, A) are ver}' active; when one of them finds an 

 egg-pod of a locust it penetrates it, and in the course of several days 

 devours two of the eggs; a period of rest follows during which it 

 molts. The second instar (Fig. 587, B) differs greatly in form from 

 the triungulin, and is known as the carahoid larva. A second molt 

 takes place after about a week, but it is not accompanied by any 

 very great change of form, though the larva is now curved, less 

 active, and in form like the larva of a scarab^eid beetle. About a week 

 later, the third molt occurs; the change in form at this molt is not 

 great, the fourth instar (Fig. 587, D) hke the third being scarabseoid 

 inform; these two instars can be distinguished as the first scarabcBoid 

 larva and the second scarabcBoid larva respectively. The second scara- 



