BLISTER BEETLES IN KAXSAS. 



19 



particular part of the country at irreg:ular intervals, and there are periods or 

 years of absolute immunity from their presence in the same regions. The young 

 blister-beetles that hatch the j-ear following the advent of the locusts in 

 immense numbers may frequently find few or no locust eggs upon which to 

 prey, and the great bulk of them would, as a consequence, porisli ; while the 

 young from such exceptional individu.ils as should not develop till two. three, 

 or more years after a locust invasion ndght stand a much better chance of 

 finding appropriate food and of thus perpetuating the species. In this case 

 and in most other cases of retarded development with which we are familiar, 

 the exceptional retardation may and does become a benefit to the species, 

 enabling it to bridge over periods of adversity. And we can see how, by the 

 preservation of such favored individuals, the habit of irregular development 

 may have become fixed in the species as a consequence of surrounding con- 

 ditions and circumstances which render it advantageous. 



/ 



Fig. 21. — Striped blister beetle {Epicauta vittata) : c, Triungullu 

 larva ; rf, second or caraboid stage ; c, same as d, doubled up as in 

 pod ; {. scarabaeoid stage ; <j, coarctate larva. All except e enlarged. 

 (After Riley.) 



In these two paragraphs Riley points out the tendency to irreguhir 

 development which is exhibited in blister beetles, and the benefit 

 which it undoubtedly is to the species. He discusses the irregularity 

 as a tendency which is already acquired, though indicating its origin 

 " as a consequence of surrounding conditions and circumstances." 

 "Whether he believed that irregular development could be induced in 

 individuals by subjecting them to certain conditions he does not 

 state. 



During retarded development the additional time involved is spent 

 in the coarctate larva stage. Ix)w temperature inhibits develoj)ment 

 in any stage, but in the other stages activity is resumed with increased 

 temperature. The hardy triungulin can survive for two or three 

 weeks without food, but Riley reports " that the first molt is usually 

 experienced about the eighth day after the first taking of food, in- 

 dicating that normal development begins with reception of nourish- 

 ment. Entering an egg-capsule automatically limits the food a 



• Kii.EY. C. v., Pack.vud, a. S., and Thomas, Cyrus. Fir.st -Xxntal Report T'. S. Ent. 

 Comm. Dept. Interior, U. S. Geol. Survey. 1877, p. 299. 1878. 



