246 
Psyche 
[December 
thick) that the wasps run out of both fluid and energy, or that the 
wasps themselves are relatively dehydrated to start with, as may 
happen when nests have been kept in heated rooms. 
A wasp ready to emerge, but still resting in its cocoon, will emit 
a drop of fluid from its mouth if disturbed by the observer, and the 
numbers of nests failing to give emergence can be greatly increased 
if each wasp, before it is ready to leave its cell, is “milked” of its 
fluid reserve. Those that do emerge after such treatment are gen- 
erally from nests with relatively thin or friable walls, or presumably 
the wasps from them are those of which at least one regained 
sufficient fluid by butchering siblings. If a wall can be readily cut, 
even though not moistenable by water, wasps will chew through it 
if the thickness is not too great. Thus A. antilope will cut its way 
out of nests in which all partitions and the terminal plugs have been 
replaced with hard beeswax walls from 2 to 4 mm or more in thick- 
ness. 
In A ncistrocerus antilope the source of the fluid is the proventricu- 
lus which, in a newly eclosed imago, will deliver from 5 mm 3 to 
more than 12 mm 3 of clear liquid. Very likely it is the proventriculus 
which supplies the fluid in all of the other cases, although that has 
not been determined. 
Davidson (1913) suggests that the cup-like caps of the very hard, 
upright cells of the nest of Pseudoniasaris vespoides collect rain which 
softens them, permitting each wasp to cut its way out. Hungerford 
( 1 93 7 ) of course threw doubt on this view when he showed that P. 
occidentalis (Cress.), the nest of which is also very refractory but 
not provided with cupped closures, emerges without a prior external 
softening of the region of exit. Actually P. vespoides itself softens 
the walls at the base of the cap of its cell from within, applying 
liquid from its mouth. It then chews away the now muddy, sandy 
coverings, turning from time to time, so that it nearly symmetrically 
enlarges a hole through the cap. It then trims the hole with its 
mandibles until it can wriggle its way out — which it does as though 
walking on the apices of its femora. In the instance observed, the 
male wasp at one point put its forelegs out through the hole, yet 
it did not try to pull itself out with them. Early during the cutting 
of the emergence hole, as the wasp turned in its cell, the left antenna 
was pushed between the mandibles. It remained there during the 
entire time (about 20 minutes) that the hole was being enlarged, in 
no way seeming to cause difficulty. 
Discussion 
The study of hatching and moulting, no less of many other aspects 
of the developmental biology of burrow-nesting eumenine wasps, is 
