THE PINE TIMBER-BEETLE. 



719 



Fig. 249. —Gnathotrichus 

 materariug. Mars del. 



" It is the habit of these timber-beetles to penetrate the tree in a 

 straight line, passing- inwards through the bark and into the sap-wood 

 to a depth of from half an inch to 2 inches, and 

 then abruptly turning they extend their burrow 

 in another straight line parallel with the outer 

 surface and at right angles with the fibers of the 

 wood, for a length of 2 to 6 inches. The only in- 

 stance in which the burrow of the species now 

 under consideration has come under my notice 

 was recently in a billet of stove wood, which un- 

 fortunately did not contain the extreme end of 

 the gallery. The annexed cut* is an exact repre- 

 sentation of this burrow, in which a live and a 

 dead beetle were found, both of them females, and 

 the only specimens of this species which have 

 come under my observation. The transverse bur- 

 row was excavated in the sap-wood at the depth 



of half an inch from its outer surface. Near its middle it was crossed 

 by another perforation extending from the outside directly towards 

 the heart of the tree, which is indicated by a black dot in the figure ; 

 and at this point the burrow curved slightly outwards towards the 

 exterior surface, as represented in the section above the principal 

 figure in the cut; and at its end on the left, where it passed out of the 

 billet of wood, it commenced curving inwards towards the heart of the 

 tree. Twelve lateral burrows of the same diameter as the transverse 

 one extended upwards and two downwards, as shown in the figure, all 

 of the same length, each one having been excavated probably by a 

 single larva. The gallery of our insect thus differs widely from that of 

 the European species (T. eurygaster Erichson) which mines in the inte- 

 rior of the pine, which has no lateral burrows branching off from it. 



"The presence of these timber- beetles in the wood can be distinguished 

 from those which mine under the bark by the little piles of sawdust 

 which they throw out at the mouth of their burrows, this dust being so 

 much more white and clean, and not composed in i)art of the brown or 

 rust colored particles of gnawed bark which are intermixed with the 

 dust produced by the bark-beetles. (Fitch.) 



The beetle. — lu addition to the short description of this beetle which is given above, 

 it may be observed that the head is finely punctured, the punctures on the face giving 

 out small pale yellowish hairs, while those on the vertex or crown are destitute of 

 hairs, and there is a slight transverse elevation of the surface between the face and 

 the vertex, from which an elevated smooth line extends backwards along the middle 

 of the vertex. Thorax, when viewed from above, with its base transverse and rec- 

 tilinear, its basal angles rectangular, its opposite sides parallel for a distance equal- 

 ing the length of the base, and from thence rounded in a semicircle at its anterior 

 end; its surface anteriorly with minute asperities, which, viewed vertically, api>ear 

 like fine transverse wrinkles ; its basal half with very minute iiunctures, and in its 

 center a small transverse tubercle. Wing-covers with fine shallow punctures in 



Not reproduced. 



