408 TERTIARY INSECTS OF NORTH AMERICA. 



Family SCOLYTIDyE Kirby. 

 HYLASTES Erichson. 



HyLASTES °? SQUALIDENS. 



PI. 1, Figs. 23-25. 

 Scoli/lidtr sj). Scndd., Can. Ent.. XVIII, 194-196 (1S86). 



Prof. G. J. Hinde sent me a branch of a conifer obtained bv liim from 

 tlie interglacial clays near Toronto on account of its being scored with insect 

 tracks. From an examination of the cell structure Dr. Gr. L. Goodale has 

 determined it to be the brancli of Juniperus communis. It is about 12..5"" 

 in length and 13 by 18"™ in thickness ; the broader surface is shown of the 

 natural size in PI. 1, Fig. 23, and the scorings, which cover a considerable 

 part of the surface, are made by several distinct tracks of a scolytid larva, 

 which appears to be referable to Hylastes, Phloeosinus, or some near ally. 

 There are parts of at least six dift'erent sets of tracks on this small frag- 

 ment, portions of all of which may be seen in the figure, and are marked 

 bv the different letters at the sides. The whole of that seen at d is enlarged 

 in Fig. 24, which shows a little more than can be seen in Fig. 23d. 



The mating chamber is more or less triangular, resembling often a 

 shark's tooth in form (whence the name) generally equiangular or tiidentate, 

 the apex upward (see especially c, d). Two of these chambers from which 

 no main galleries take their rise occur on the stick ; they may, however, 

 have some other explanation, since they are much narrower and much more 

 deeph' excavated than the other mating chambers. Possibly they were 

 unsatisfactory to the constructor and left unfinished. 



From the mating chambers, which are not deep and are about 3™™ in 

 diameter, pass the main galleries ; these generally run obliquely, but more 

 nearly transverse than longitudinal (as in Fig. 24), are subequal, and take 

 their rise one on either side of the mating chamber at the lateral angles and 

 run in exactly or almost exactly opposite directions. In one case, however 

 {d), there is but one main gallery, and in another (/) they are at right angles 

 to each other, one being longitudinal ; but in this latter case the mating 

 chamber is in the reverse of the usual position, the apex being downward. 

 These main galleries vaiy from 1.5 to 8™'" in length, and are slightly more 

 than a millimeter wide, with dentate edges, marking probably the sinuses 

 where the eggs are laid by the parent. 



