288 Transformations and Habits of Blister-Beetles. [ May, 
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 (Pl. 1., 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 Apzcauda forcibly recalls the mature 
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 larvæ 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 in- 
teresting 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 £. 
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 Æ. vittata to occupy 
but 24 days. As this species occurs in the beetle state as early 
as June in the latitude of St. Louis and as late as October, there 
are possibly two annual generations here and farther south. 
Larval Habits of Macrobasis and Henous—The characteristics 
of the triungulins of the blister-beetles, represented by Zpicauta 
and Henous, are remarkably similar, and point to unity of habit. 
The same holds true of the characters of the second, coarc- 
tate and third larva and of the pupa of Epicauta and Macrobasis. 
They are precisely alike; so that, while appreciable differences 
may be found in the triungulins, it is doubtful whether the subse- 
1An insect is not properly parasitic that simply feeds on eggs, but the term is per- 
missible and even necessary to characterize and distinguish those species which de- 
velop within and are confined to a locust egg-pod, from the predaceous species that 
are not confined but pass from one pod to another. 
