Severin and Sever in—Habits of the Saw-fly. 73 
moult, the head and body are of a light yellowish color, with a 
darkened region extending along the dorsal median line of the 
body. The darkened region is probably due to the contents 
of the alimentary canal. The larva after moulting measures 
between eleven and twelve millimeters, when the body 1 © 
stretched out. A day later, the larvae w r ere again found to be 
covered with a white, flaky substance. As the life history of 
Gimbex americana is well known, no attempt was made to fol¬ 
low the larvae further than the first moult. 
INJURY TO THE WILLOWS. 
If one wishes to know whether specimens of Cimbex amen - 
cana are found in a certain locality, all that is necessary is to 
examine the branches of various species of willows, and if 
rough gashes extend transversely or nearly so around the limbs, 
one may be certain that this insect is the cause of the injury. 
These gashes, which the saw-flies cut with their strong mandi¬ 
bles, extend spirally around the terminal twigs (Fig. 3, sc), but 
around the somewhat thicker branches the incisions often ex¬ 
tend completely around the limb (Fig. 3, ic ), or more often a 
little more than halfway around the twig, or there may be a 
number of smaller incisions one above the other. The inci¬ 
sions generally extend through the bark and may be cut a 
slight distance through the wood. 
An examination of some of the branches one to three or 
four years after the injury shows that the incisions have al¬ 
ways healed over, although sometimes a splitting of the bark 
may have occurred at the place of injury (Fig. 4, b). The 
tree continues to grow, apparently without being injuriously 
affected. In only a few cases did we notice branches broken 
at the incisions, although if one bends a branch which Cimbex 
has attacked, it always breaks at the incision, and often with 
little exertion. 
What can be the object of cutting these incisions in the 
twigs? Comstock (1) writes as follows:—“These saw-flies 
have been known to injure willows by biting incisions half-way 
around the terminal twigs of the tree. What their object was 
