222 
THE STUDY OF INSECTS. 
the burrow made by the larva. When ready to change to 
an adult, the pupa works its way partially out from its bur¬ 
row. This is accomplished by means of backward-project¬ 
ing, saw-like teeth, there being one or two rows of these on 
each abdominal segment. After the moths have emerged 
the empty pupa-skins can be found projecting from the 
deserted burrows. 
The Carpenter-moths are of medium or large size. Our 
more common species are of a pepper-and-salt color, due to 
strongly contrasting dark and light scales. The antennae 
are usually pectinate in both sexes, but in some species those 
of the female are simple ; the ocelli are wanting; and the 
mouth-parts are obsolete. 
The structure of the wings is shown in Figure 255 
There are two anal veins in the fore wing, and three in the 
hind wings. The base of vein V is preserved, and is forked 
within the discal cell. In the fore wings, the branches of 
vein III anastomose so as to form an accessory cell. The 
frenulum is rudimentary in most of our genera (Fig. 255), 
but is strongly developed in others. 
Our most common species is the Locust-tree Carpenter- 
Fig. 256. —Prionoxystus robinia. 
moth, Prionoxystus robinice (Pri-on-ox-ys'tus ro-bin'i-ae); 
Figure 256 represents the female natural size. The male is 
but little more than half as large as the female. It is much 
