Lire History oF AN OAK Twic GIRDLER 17 
Eccs. The eggs are usually laid singly on the side of the twig 
near the terminal bud. Sometimes they are laid an inch or more from 
the terminal bud on last year’s wood, as shown in Fig. 3 of Plate I. 
As soon as laid, the egg spreads out like a little pancake and adheres 
firmly to the bark. These have been taken, still sticking securely to 
the bark, two years after being laid. The eggs hatch in about ten 
days. When first laid they look like a small flattened piece of green 
gelatine. They soon turn brown and after hatching the shell becomes 
gray. 
LarvaE. First instar. When hatching the young larva makes its 
way out of the eggshell directly into the bark beneath the egg. Newly 
hatched larvae were first found July 24. The larvae immediately begin 
encircling the twig beneath the bark. By August 7 trees all over 
the cities showed signs of infestation. As 
the burrowing continued more leaves were 
cut off. Often the burrowing continued to 
the junction of the original twig with a 
larger branch and around the larger branch 
thus cutting off the nourishment from all the 
twigs above this burrow. Consequently all 
the leaves on the upper part of the larger 
branch soon died. Thus one larva was re- 
sponsible for the dying of many leaves. 
During the rest of the month of July and 
in August and September of the first year 
the larvae confine themselves to the cam- 
bium layer. The burrows at this time were 
of uniform diameter and the head measure- 
ment of the larvae was 0.375 millimeters. 
Second instar. In May and June of the 
next year the larvae still confined them- 
selves to working just under the surface 
bark. The head measurements at this time 
averaged 0.47 millimeters. 
Third and fourth instars. The larvae 
were actively at work during July, August 
and September of the year following hatch- 
ing, for the most part burrowing in the 
centezwotethe twies, lo’ the middle of 
- Fig. 2. The bark on an oak 
USS cMemieade measurements averaged (hy 2A et ane sa anne ea 
07 millimeters whileatter that'date they — wavgre: tanvae (tm thet: bur. 
