6CUDDER.] CANADIAN FOSSIL INSECTS. 29 



tracks. Fi'om 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"" in length and 13 by IS"™ in thickness; 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 different 

 sets of tracks on this small fragment. 



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

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

 tate, the apex upward. 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 inuch narrower and much more deeply 

 excavated than the other mating chambers. Possibly they were unsatis- 

 factory 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, 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, 

 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""" in length, and are slightly 

 more than a millimetre wide, with dentate edges, marking probably the 

 sinuses where the eggs are laid by the parent. 



At least this is the custom with the mining beetles ; but here, as in 

 some other rare cases, the young larv;v do not begin to mine at right angles 

 to the main gallery, but all start from one spot, either the summit of the 

 mating chamber or the extremity of one of the main galleries, and thence 

 burrow in irregular and somewhat interlacing mines in a longitudinal 

 direction, but nearly all apparently either upward or else downward, not, 

 as usually, in the two directions almost equally. Apparently they may 

 often turn upon their course again and again, or they may mine in an 

 almost perfectly straight line or in a tortuous line for as much as 5™' in 

 the whole of which distance the mine will scarcely have doubled in 

 width ; indeed, in many cases it is difficult to tell in which direction the 

 larva has moved. The greatest width of these mines is scarcely more 

 than half a millimetre, and they vary greatly in depth. 



The connection between the main gallery and the mines is often obscure, 

 owing doubtless to the younger larva? burrowing more in the bark than 

 in the wood (the bark being here entirely lost). In one case there is a 

 mating chamber and a pair of short galleries, but nothing more ; here 

 apparently the mother fell a prov to some enemy before oviposition. 



