54 
Psyche 
[April 
without biting the skin of its prey and its feeding is indicated 
only by the rhythmic movement of its body, but as it increases 
in size it may be seen to bite rather ferociously at its caterpillar, 
sinking its mandibles and even its entire head into the now 
lacerated body. Growth is rapid and usually the food is con- 
sumed to the last bit, even the heads being eaten by some of the 
more voracious individuals. When all the food is gone the larva 
may be observed moving about its cell, its mandibles constantly 
working along the walls. Whether it is searching for more food 
or attempting to begin its cocoon is not entirely evident. At 
any rate, the result of this activity seems to be that all the de- 
tritus in the cell, including the excrement of the caterpillars and 
whatever of the food supply may occasionally remain uneaten, 
becomes gathered at one end or along the lower wall of the cell, 
so that it does not interfere with the spinning of the cocoon. 
Before actually spinning the cocoon the Ancistrocerus larva 
makes a rather coarse-meshed network closely applied to the 
walls of the cell, entirely lining it and excluding all debris. The 
cocoon is variable in shape, irregularly cylindric-elliptical with 
one of its ends and its lower surface touching the walls of the 
cell, usually at the inner and lower end. It is tough, closely 
woven, translucent and semi-transparent, usually of a pale 
brownish tint with a slight silky lustre. Figure 2, though per- 
haps of a different species, illustrates the position of these 
cocoons in situ. Pupation does not take place immediately, the 
larva remaining quiescent in the cell for from five to seven days. 
As in most nidificating Hymenoptera which construct 
similar nests, the outermost occupant of the nest is the first to 
emerge, though it is necessarily the product of the most recent 
egg laid by the builder. All the males reach the adult stage at 
about the same time, but until the one nearest the entrance 
makes its escape, there appears to be no attempt on the part of 
the others to break out, though they often may have already 
broken from their cocoons and are free to emerge as soon as the 
way is clear. Once the first male has made its escape the others 
follow in rapid succession, the females only remaining after the 
males have been gone for some little time. 
