84 



The Genus Trypodendron Stephens. 

 Stephens, 111. Brit. Ent., 3: 353, 1830. 



Xyloterus Er. 



Erichson, Wieg. Archiv., 1:60, 1836. 

 Key to the Species. 



A The'jf'eltyra strongly and regularly striate, and rather coarsely punctured; 

 the declivity with the second interspace normal, not sulcate; the 

 pronotum asperate-punctate on the sides behind. D.C., Pa., W. Va., 

 N.Y., N. Mex. scabricollis Lee. 



AA The elytra at most rather faintly striate, the striae usually somewhat 

 irregularly punctured; the declivity with the second interspace 

 depressed to form a distinct sulcus; the pronotum finely punctured on 

 the sides behind. 



B The carina forming the lateral margin of the declivital sulcus wide 

 and irregularly punctured, the pronotum entirely black, closely 

 granulate on the median part of the disc behind; the elytral declivity 

 distinctly hairy. 



C A larger species, 3-5 mm-4 mm.; the declivital sulcus wide and 



deep, gradually narrowed on the caudal half; the elytra with 



brilliant lustre, the interspaces usually flat; the male with the 



cephalic margin of the pronotum broadly emarginate as viewed 



from above. Populus. retusus Lee. Page 85. 



CC Length, 3 mm. to 3-5 mm.; the declivital sulcus rather narrow 



and its sides nearly parallel; the elytra with rather dull lustre, 



the interspaces usually noticeably convex; the male pronotum 



broadly arcuate in front. Betula. betulae Sw. Page 85. 



BB The carina forming the lateral wall of the declivital sulcus narrow 



and uniseriately punctate or granulate-punctate; the pronotum 



punctured across the middle line near the caudal border, at most 



but sparsely granulate; the declivity sparsely and indistinctly hairy. 



C Interspace 2 of the declivity distinctly punctured and usually 



as wide as interspace 1 and interspace 3, which are distinctly 



granulate; the pronotum and elytra normally marked with pale 



bands. 



D The punctures of the elytral striae rather deep and usually 

 rather coarse; the discal pale area of the pronotum usually 

 extending from the base to the cephalic margin. British 

 Columbia west of the Rockies, cavifrons Mannh. Page 85. 



PLATE 19. 

 IPID TUNNELS (ORIGINAL). 



Fig. 1, Dryocoetes confusus Sw.; Tunnels in balsam, inner surface of the bark; three-fifths 



natural size. 

 Fig. 2, Dendroctonus borealis Hopk., Tunnels in white spruce, inner surface of the bark, showing 



?arasitized larvae; about one-half natural size. 

 _ , ps perturbatus Eichh.; Tunnels in white spruce, inner surface of the bark; much reduced. 

 Fig. 4, Pityophthorus canadensis Sw.; Tunnels in a white pine twig, surface of the wood; four- 

 fifths natural size. 



