RILEY LARVAL HABITS OF 3LISTER-BEETLES. 555 



insect has the power of remaining in this coarctate larval condi- 

 tion for a long period, and generally thus hybernates. 



In spring the coarctate lai-val skin is, in its turn, rent on the 

 top of the head and thorax, and there crawls out of it the Third 

 Larva,* which differs in no respect from the ultimate, stage of the 

 second larva already mentioned, except in the somewhat redu- 

 ced size and greater whiteness. The coarctate skin, when deserted, 

 retains its original form almost intact. The third larva is rather 

 active, and burrows about in the ground ; but while there seems 

 to be no reason why it should not feed, nourishment is not at all 

 essential, and all my specimens have, in the course of a few days, 

 transformed to the true pupa without feeding. In the transforma- 

 tion to pupa (PI. v., Fig. 9) the third larval skin is worked into 

 a wrinkled mass behind, as is also the skin of the true pupa when 

 shed. The pupa state lasts but five or six days, and before the 

 wings of the imago are fully expanded, or the abdomen con- 

 tracted, the general aspect of Epicauta forcibly recalls the ma- 

 ture Henous. 



Like all parasitic! insects that nourish on a limited amount of 

 food and possess no power to secure more, the blister-beetles vary 

 greatly in individual size in the same species, and the larvae have 

 the power of accommodating their life to circumstances, and of 

 assuming the coarctate larval form earlier or later according to 

 the size of the egg-mass which they infest. I have had some 

 interesting illustrations of this in my experiments with them In 

 an average sized egg-pod of the Differential Locust, however, 

 there are more than enough eggs to nourish the largest specimen 

 of E. vittata, and a few are usually left untouched. 



The period of growth, from the first feeding to the coarctate 

 larva, averages, as will be gathered from the foregoing, about a 

 month ; yet in the month of September, out-doors, under screens 

 where I have had the Differential Locust oviposit for the experi- 

 ment, I have known the full larval growth of vittata to occupy 



* The coarctate larva is, properly speaking, the third and that following it the fourth; 

 but just as I have preferred to designate as special stages of tlie second lar\-a the stages 

 between the first and fourth molts, so I prefer to call the last larva the third, to conform to 

 the nomenclature now generally employed. 



t An insect is not properly parasitic that simply feeds on eggs, but the term is permissi- 

 ble and even necessary to characterize and distinguish those species which develop within 

 and are confined to a locust egg-pod from the predaceous species that are not confined but 

 pass from one pod to another. 



