F. R Browne 353 
IV. Life-history. 
{a) General statement. 
Various facts in the life-history have been given by different authors but 
there are only two accounts which are in any way complete, those of Malyshev 
(1911) and of Graham Smith (1915-16 and 1917—18). The former author deals 
with the species as a parasite of Odynerus, a genus of solitary diplopterous 
wasps, while the latter deals with it as a parasite of certain Diptera. 
Malyshev’s observations and experiments go farther than those of Graham 
Smith but in one or two important points they are incomplete. In view of 
the fact that Malyshev’s paper is in Russian, I offer no excuse for giving here 
a detailed account of the life-history. 
So far as I have observed, the imagines first appear under natural conditions 
some time after the middle of May and they can be found in their haunts as 
late as September. Under laboratory conditions, by keeping the species in 
an incubator at summer temperatures, it is possible to continue to produce 
successive generations throughout the winter, and this fact has enabled me 
to complete and repeat certain experiments which otherwise would have 
taken perhaps six or seven months (see Chap. XII, “Winter rearing of 
Melittobia ,” p. 367). 
Although occasional over-wintering pupae are to be found the species 
normally winters in the larval condition and although, as I have said, the 
imagines may appear in May, overwintered larvae may remain as larvae until 
June, the imagines not appearing until July, even when kept in the laboratory. 
These hibernating larvae are not always full-grown but as many batches of 
such larvae have completely finished their food supply before commencing 
hibernation, they either complete their growth by feeding upon their neigh¬ 
bours in the mass or perhaps in some cases pupate prematurely. 
It might also be reasonably assumed that any food left over would be 
unfit for consumption by the time the larvae became active again but this is 
not necessarily the case as the host larva remains alive for a long time during 
the process of “deflation.” 
Under natural conditions, shortly after emergence, the females, having 
mated, break out of the cells in which they have developed. At this stage 
they show a definitely positive heliotropism. Such individuals, released in 
front of a window in the laboratory, move directly towards the light and, if 
confined in a horizontal glass tube closed at one end, they will remain in the 
tube if the open end is turned away from the source of light. If such a tube 
is turned round, the females at once stream out towards the light. 
This positive phototropism lasts for a considerable time but it is ap¬ 
parently eventually overcome by a chemiotropism when the insects seek the 
cells of their hosts, primarily for nourishment. 
The first tendency of the female on entering the cell of a host is to feed, 
although oviposition upon the host may commence very soon. 
