1966] 
Cooper — Eumenine IVasps 
239 
There is an earlier point too inf the life of each wasp at which, if 
it is to survive, it must likewise break out of an enclosure the walls 
of which it did not make. This first passage is of course prelude to 
the onset of active larval life, being penetration of the tough chorion 
or “egg shell”. It is my aim to show how each of these escapes is 
accomplished. So far as I can discover, only Nielsen (1932) has 
disclosed the special aspect of exit from a masoned nest, and this in 
a species of * Symmorphus. The means of escape from the chorion 
seems a wholly new observation, even though the mechanism may 
prove to be widespread among Hymenoptera. In addition I shall 
show that these wasps have a fixed number of larval moults, an aspect 
of the biology of hunting wasps about which there has been consider- 
ably uncertainty. The records which now follow have all been made 
from broods originally established by mother wasps in “trap nests”. 
1. Hatching of Ancistrocerus antilope (Panz). 
When a newly completed, provisioned cell of Ancistrocerus anti- 
lope is opened, just as with most other eumenids, the cream colored, 
slightly bowed, elongate and turgid egg is normally found above or 
among the paralysed prey. In either case, the blunt caudal end of the 
egg: is firmly attached to the ceiling of the cell by a short, flexible 
suspensory thread that is from 0.5 to 0.8 mm long and 14-16 /x in 
diameter (fig. 1). The egg itself is about 2. 7-2. 8 mm long by 0.8 
to 0.9 mm wide, rather small for a eumenid’s egg to judge from the 
sample of eggs of 13 species measured by Iwata (1955). When 
fresh, the chorion is tough, seemingly inelastic, and leathery to manip- 
ulation by forceps, even though very thin. At 20°C, the egg hatches 
some 2 to 4 days after it is laid (Cooper 1953). 
Shortly before hatching occurs, the brownish tips of the mandibles 
and the segmentation of the body of the larva can just be seen through 
the chorion. The first larval movements that I detected were of the 
forebody, and mandibles. Thereafter they may include intermit- 
tent gentle squirmings of the entire body. The larva evidently takes 
up most of the fluid lying between it and the envelope of the egg 
during its first exertions, for the still intact chorion now everywhere 
becomes closely appressed to the larva, and may then follow the 
contours of the larva’s body segments as Taylor (1922) has ob- 
served. Three denticles, at the levels of the 4th, 5th and 6th post- 
cephalic segments of the larva, thereupon burst the chorion on each 
side of the egg, minute amounts of fluid escaping when this happens. 
The caudal third of the chorion collapses and shrivels, forming two 
or more folds that radiate lengthwise from near the base of the sus- 
pensory filament, reducing the free space at the caudal pole of the 
egg (fig. 2). 
