4G8 TERTIARY INSECTS OF NORTH AMERICA. 



Family SCOLYTID^E Kirby. 



HYLASTES Erichson. 



HYLASTES I SQUALIDENS. 

 I'], l, Figs. i':j-L'5. 



Seolylidw sp. SciuUl., C'au. Ent.. XVIII, 194-11)6(1836). 



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

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

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

 determined it to be the branch of Juniperus communis. It is about 12.5 CIU 

 in length and 13 by 18 mm 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, Phlceosinus, or some near ally. 

 There are parts of at least six different sets of tracks on this small frag- 

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

 by 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 tridentate, 

 the apex upward (see especially r, <l). 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 

 deeply excavated than the other mating chambers. Possibly they were 

 unsatisfactory to the constructor and left unh'nished. 



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

 (rf), 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 vary from 1.5 to 8 mm in length, and are slitrhtlv more 



J */ 



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

 where the eggs are laid by the parent. 



