444 Larval Habits of Bee-Fties. [June, 
wasp that had made use of the burrows of a bee (Anthophora 
abrupta Say). The larva of Argyramceba has very much the 
same appearance as that of Systcechus and Triodites, and the 
pupa is distinguished from the pupa of this last (PI. v1, Figs. 5, 
5 a), principally by its longer and more numerous hairs, longer 
anal spines, and more conspicuous spiracles. 
Systropus also, in the larva state, preys on the larva of Lima- 
codes, as has been observed by Walsh (Proc. Bost. Soc. N. H. 1x, 
300), and by Westwood (Trans. London Ent. Soc., 1876, p. 571); 
killing its victim only after the latter has formed its tough cocoon. 
With these general remarks, we will now give a more full and 
descriptive account of the two bee-flies which, by rearing from the 
larva, we know to have this locust-egg-feeding habit. Our plate 
illustrates the insects as well as can be done in color printing, but 
the enlarged heads of the larva should be somewhat darker and 
less yellow. 
SysTasCHUS OREAS.—The character of the eggs and the manner 
in which they are laid have not yet been observed. The larva (Pl. 
vi, Fig. 1) is found in the locust egg-pods, or near them, of differ- 
ent sizes, during most of the year. These larve begin to trans- 
form to the pupa state early in the summer, and the pupa (Pl. v1, 
Fig. 2) pushes itself half way out of the ground in order to dis- 
close the fly. These flies continue to issue during the summer 
months, As a rule, but one year is required for full development, 
but there is, in this respect, great irregularity, and the same ten- 
dency to retardation which we have called attention to in the case 
of the blister-beetles! We have had quite a number of the larve 
remain over unchanged till the second year, and all that we have 
said as to the philosophy of this retardation in the one case 
applies in the other.2. Weare inclined to think that future obset- 
1Am, Entomologist, 111, 196. 
2 This irregularity in the development of individuals is noticeable in many insects 
that are parasitic, and whose mode of life is precarious. In the case of our blister” 
beetles, depending as they do on locust eggs, and especially in the case of 
which feed particularly on the eggs of migratory species, it is not difficult Je per 
ceive how this trait may prove serviceable to the species possessing it. Migratory 
locusts occur in immense numbers, in some particular part of the country, 
intervals, and.there are periods or years of absolute immunity from their pre 
same regions. The young blister-beetles that hatch the year following the ; 
the locusts in immense numbers may frequently find few or no locust eggs upon 
to prey, and the great bulk of them would, as a consequence, perish; while t 
young from such exceptional individuals as should not develop till two, three, OF 
