534 HYMENOPTERA. 



part of the 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 



* Introduction to the Modern Classification of Insects, Vol. II. p. 118. 



