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- 

 cerued in the ravages of spruce forests iu 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 pupse, 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 Xylehorus 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 couipletely 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 mouth 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 (Rhynchophora, p. 357), the club of 

 the antennae is oval, compressed, and solid, 

 without articulations; the shining corne- 

 ous part extends forwards in a narrow baud 

 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 fuuicle is 

 composed of two parts as in the two preced- fig. ii^.-xyioteres uvutatus—a. an- 

 iug genera; the first joint is large, and stout i^ed -Gisfier '27"'' ^"'"''' 

 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 fuuicle to be 4-jointed. 



