534 
HYMENOPTERA. 
part of tlie body, and are provided with strong and pow¬ 
erful jaws, wherewith they bore long holes in the trunks 
of the trees that they inhabit. Like other borers, these 
grubs are wood-eaters, and often do great damage to pines 
and firs, wherein they are most commonly found. 
When fully grown, the grubs make thin cocoons of silk, 
interwoven with little chips, in their burrows, and in them 
go through their transformations. The chrysalis is some¬ 
what like the winged insect in form, but is of a yellowish 
white color till near the time of its last change, and the 
wings and legs are folded under the breast; in all these 
respects it agrees with the chrysalids of other Hymenop- 
terous insects. After the chrysalis skin is cast off, the 
winged insect breaks through its cocoon, creeps to the 
mouth of its burrow, and gnaws through the covering of 
bark over it, so as to come out of the tree into the open 
air. It is stated that the grubs of the large species come 
to their growth in seven weeks after the eggs are laid. 
If this be true, and it seems hardly possible, the chrysalis' 
state must last a long time, for the perfected insects have 
been known to come out of timber that had been cut up 
and applied to mechanical uses by the carpenter. Some 
persons have supposed that they attacked only diseased and 
decayed trees, in which it must be admitted they are often 
found in great numbers. But many instances might be 
mentioned of their appetite for sound wood also, and it is 
probable that the presence of these insects, like that of 
many others, is the cause, and not the consequence, of the 
decay of the trees wherein they live. 
It is stated in the London “ Zoological Journal,” that 
two hundred Scotch firs have been destroyed by the Uro- 
cerus Juvencus^ in the woods of Henham Hall, the seat of 
the Earl of Stanhope, their trunks being bored through 
and through by the grubs of this insect. Mr. Westwood 
relates,^ that a piece of wood, twenty feet in length, from 
* Introdiiction to the Modern Classification of Insects, Vol. II. p. 118 . 
