226 NATURAL HISTORY OF WASPS. 
prevent it turning its head in its cell so as to reach 
the bottom, and the covering would only extend 
half-way down. And the insect would come out 
crippled, because the juices of the pupa had evapo- 
rated too rapidly. However, in the regular course 
of things, the larva eats and grows, and while it 
grows it spins the lining to its cell. At first it seems 
to do nothing but eat, but at last it gives up eating 
altogether, and only spins. The head is no longer 
put out asking for food, but moves about just like 
that of a caterpillar spinning its cocoon. And, as 
we watch, a round white cap rises high over the 
paper margin of the cell; the larva retires from 
sight; and the nurse-wasps transfer their attentions 
to other little heads which peep forth from the outer 
rings of the comb. 
The larva now casts its skin a second time. In 
the first moulting only the skin was shed, but in the 
second, not the skin only, but such parts of the 
larval body as the perfect insect will not require are 
cast off. Among these. are the second pair of de- 
ciduous mandibles. Who can enter far enough into 
the secrets of a wasp’s infancy to say what is the 
use of the long central tooth in its first pair? 
Surely, if the larva had set out on its travels 
thus equipped, one would have found a use for 
this pointed tooth in hanging on to the cell-wall. 
But the second pair have the three teeth all of nearly 
Fig. 12.—Successive forms of the Man- 
dibles. 
‘ 1. Of the larva in its first skin. 
3 2. Of the larva in its second skin. 
’ 2 3. Of the perfect insect. 
P The relative proportions have been care- 
fully preserved. 
