6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 52 



B. GNATHOTRICHUS MATERIARIUS FITCH 



1859. Fitch, Asa(i). 



Original description : 



Pine Timber-Beetle. Tomicus niateriarius, new species. In the interior of 

 the sap wood, mining slender straight cylindrical burrows in a transverse 

 direction, parallel with the outer surface, from which very short straight 

 lateral galleries branch ofif at right angles above and below; a rather 

 slender cylindrical black shining bark-beetle, 0.15 long, with pale dull 

 yellow legs and antennae, the fore part of its thorax and of its 

 wing covers tinged with reddish yellow; the thorax equalling two-thirds 

 the length of the wing covers, with a small elevated tubercle in the 

 middle, forward of which it is rough from minute elevated points; the 

 wing covers with rows of minute punctures, their tips rounded, the upper 

 part of the declivity with a shallow longitudinal depression or groove 

 along the suture, forming a slight notch. 



The insects belonging to the genus Tomicus and kindred genera of the same 

 family by their habits divide themselves in^o two distinct groups. The 

 larger portion of them reside in or immediately beneath the bark of 

 different trees and are currently termed bark-beetles. But this designation 

 is inappropriate for another portion of them which dwell in the interior 

 of the wood, and there excavate their galleries. The name timber-beetles 

 appears to be the most appropriate for these. Another point in which, 

 from the observations of M. Ferris, these two groups appear to differ 

 in a remarkable manner, is the relative numbers of the two sexes. With the 

 bark-beetles there are commonly several males in company with but one 

 female, and the former appear to perform the chief part of the labor in 

 the excavation of their galleries. With the timber-beetles, on the other 

 hand, the females are the most numerous, and probably mine their galleries 

 without any assistance from the other sex. M. Ferris states of one of 

 the species, that upwards of fifty females were met with in the burrows 

 they had excavated, without a single male being found there. 



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 two inches, and then abruptly turning they extend 

 their burrow in another straight line parallel with the outer surface and 

 at right angles with the fibres of the wood, for the length of two to six 

 inches. The only instance in which the burrow of the species now under 

 consideration has come under my notice, was recently, in a billet of stove 

 wood, which unfortunately did not contain the extreme end of the gallery. 

 The annexed cut is an exact representation of this burrow, in which 

 a live and dead beetle were found, both of them females, and the only 

 specimens of this species which have come under my observation. The 

 transverse burrow was excavated in the sap wood at a 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 toward the exterior surface, as repre- 

 sented 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 



