196 INSECT ARCHITECTURE. 



Among the carpenter-grubs may be mentioned 

 that of the purple capricorn-beetle (Callidium viola- 

 ceum), of which the Rev. Mr. Kirby has given an 

 interesting account in the fifth volume of the Lin- 

 nean Transactions. This insect feeds principally 

 on fir timber, which has been felled some time with 

 out having had the bark stripped off"; but it is often 

 found on other wood. Though occasionally taken in 

 this kingdom, it is supposed not to have been ori- 

 ginally a native. The circumstance of this destruc- 

 tive little animal attacking only such timber as had 

 not been stripped of its bark ought to be attended 

 to by all persons who have any concern in this article; 

 for the bark is a temptation not only to this, but 

 to various other insects; and much of the injury 

 done in timber might be prevented, if the trees were 

 all barked as soon as they were felled. The female 

 is furnished, at the posterior extremity of her body, 

 with a flat retractile tube, which she inserts between 

 the bark and the wood, to the depth of about a quar- 

 ter of an inch, and there deposits a single egg. By 

 stripping off the bark, it is easy to trace the whole 

 progress of the grub, from the spot where it is 

 hatched, to that where it attains its full size. It first 

 proceeds in a serpentine direction, filling the space 

 which it leaves withits excrement, resembling sawdust, 

 and so stopping all ingress to enemies from without. 

 When it has arrived at its utmost dimensions, it does 

 not confine itself to one direction, but works in a kind 

 of labyrinth, eating backwards and forwards, which 

 gives the wood under the bark a very irregular sur- 

 face; by this means its paths are rendered of con- 

 siderable width. The bed of its paths exhibits, when 

 closely examined, a curious appearance, occasioned 

 by thegnawingsofitsjaws, which excavate an infinity 

 of little ramified canals. When the insect is about to 

 assume its chrysalis state, it bores doi*n obliquely 



