SPRUCE BARK-BEETLES. 823 
1. The unarmed spruce bark-borer. 
Xyloteres bivittatus Kirby. 
Order Coleoptera; family Scolytid^:. 
(Larva, Plate xxiv ; fig. 1 ; pupa, la.) 
This is the most destructive pest of the spruce, the beetle most con- 
cerned in the ravages of spruce forests in northern New England from 
1878 to 1881. We first observed it July 22, 1881, in spruce, stumps near 
the Glen House, in the White Mountains, N. H., the tree having evi- 
dently been cut down within a few months ; the beetles were very 
abundant, and though there were no perforations in the bark, there 
were small holes between the bark and the wood on the top of the 
stump, the beetles having availed themselves of the shrinkage of the 
bark due to drying of the wood, to effect an entrance between it and the 
wood itself ; here they were congregated in abundance and were appar- 
ently engaged in making the primary galleries of their mines and lay- 
ing their eggs. It was also found under the bark of dead standing or 
fallen spruces. Afterwards (July 27) this bark-borer was found in 
abundance, many larvae, a few pupae, and beetles in great numbers, 
under the bark of partly living and dead spruces at Brunswick. The 
burrows made were small and irregular, slightly larger than the size of 
the beetle, and were much like those made by Xyleborus ccelatus, with 
which it was commonly associated. It was also found at Merepoint. 
The trees at Brunswick teemed with them, and many fewer beetles than 
those observed would suffice to completely girdle and kill the tree. 
This beetle has its insect enemy; we observed a green chalcid fly un- 
der the bark, July 27, and a month later, August 25, chalcid larvae 
nearly fully grown were found under the bark so near the larvae of this 
beetle, that we feel justified in supposing that it must have been feed- 
ing on them. (See Plate xxiv; figs. 6, 6a,) 
In the genus Xyloteres, according to Le- 
conte (Bhynchophora, p. 357), the club of * J^P* t 
the antennae is oval, compressed, and solid, <} 0$£k $ 
without articulations; the shining come- *f . ."'■ 
ous part extends forwards in a narrow band 
as far as the middle, except in X.politus, 
where it is entirely basal, and the club is 
indistinctly divided by one round suture ; 
the rest of the surface is opaque, finely 
pubescent, and sensitive. The funicle is 
Composed Of tWO partS as in the tWO preced- Fig. 276. -Xyloteres bivittatus— a. an- 
ing genera; the first joint is large, and stout IXUd -Gissierd^^ ^^^ 
as usual, the remaining part is about equal 
in length, forming a pedicel to the club, and is divided by two not well 
marked transverse sutures, thus causing the funicle to be 4-jointed. 
