1966] 
Cooper — Eumenine Wasps 
243 
At hatching, when the larva has taken up the fluid enclosed by 
the intact chorion and commences to creep, it is quite likely that the 
spines and laminate denticles of the thoracic fields of each side as- 
sist chiefly in the pushing and creeping movements of the larva by 
gaining purchase against the chorion ; in doing so, they probably no 
more than abrade the inner face of the chorion, for they do not ap- 
pear to penetrate it. It is quite otherwise, however, with the compact, 
high multidentate teeth of the first three abdominal segments. 
Drawn forward against the appressed chorion, ratchet like, the 
strongly projecting teeth of the first three abdominal segments must 
receive litle resistance. But when moved rearwards as the larva 
squirms forward, their spines and blades thrust into the chorion, 
perforating, tearing and sawing it in the manner I have described. 
Once the chorion is slit open along each side of the middle third of 
the egg, those spines of the thoracic fields which are directed forward 
or laterally very likely engage the anterior end of each lateral rift 
as the larva alternately elongates and contracts, thereby extending 
the tear in the chorion still further forward. 
There can be little question that all of these fields of spines are 
adaptations solely related to hatching, for they are present on the 
cuticle of the first instar larva only, and are shed with that cuticle 
at the first moult. Indeed the integument of the second instar has no 
vestige or reminder of either the specialized fields of spines of the 
thorax or of the composite teeth of the first three abdominal segments 
that so effectively rip the egg open at the onset of independent larval 
life. These structures are therefore ruptor ovi (or “egg bursters”) 
in the strictest sense, and their presence marks the larval development 
of A. antilope as hypermetamorphic. 
3. The number of instars 
For more than a century there has been uncertainty and dispute as 
to whether hunting wasps normally have a fixed number of moults, 
hence of instars, in their development. So far as eumenine wasps are 
concerned, the uncertainty is very likely due to the fact that, sooner 
or later, most cast larval exuvia are nearly always eaten by the wasp 
larva as it feeds. The exuvium peels back to the tacky or viscid 
caudal end of the larval wasp at ecdysis, with the exoskeleton of the 
head capsule, split along its median suture, projecting from the ven- 
tral surface of the last abdominal segments of the larva. The exuvium 
is then generally held there as the larva, by arching its body and 
pushing with its abdomen, presses the prey against its mouth. As 
the last remnants of a caterpillar are eaten, so also are any moults 
