THE CANADIAN ENTOMOLOGIST. 195 



upward. From two of these chambers no main galleries arise ; there 

 may be some special reason for this, since they are much narrower and 

 much more deeply excavated than the ordinary chambers ; they were 

 perhaps unsatisfactory to the constructor and left unfinished. 



From the other mating-chambers, which are about three millimetres in 

 diameter, the main galleries generally run obliquely, but more nearly 

 transversely than longitudinally to the stem ; they are subequal and take 

 their rise one on each 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 perpendicular ; in this latter case, the 

 mating-chamber is reversed, the apex being downward. These main gal- 

 leries vary from one and a half to eight millimetres long, and are slightly 

 more than a millimetre wide, with dentate edges, where the eggs were 

 probably laid by the parent. 



At least this is the general custom with the Scolytidae ; but here, as in 

 some other rare cases, the young larvae do not commence to mine, each 

 at right angles to the main gallery, but collect together and all start from 

 one spot, the summit of the mating-chamber or the extremity of one of 

 the galleries, and thence burrow in irregular and somewhat interlacing 

 mines along the stem, and all apparently either upward or else down- 

 ward, not, as is usually the case, in both directions ; 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 half a decimeter. 

 In that whole distance the mine will scarcely have doubled in width with 

 the growth of the larva, and in many cases it is difficult to tell in which 

 direction the larva moved. The greatest width of these larval 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 larvse burrowing, while young, more in the bark than in 

 the wood. In one case there is a mating-chamber and a pair of short 

 galleries, but nothing more ; here, apparently, the mother fell a prey to 

 some enemy before accomplishing her purpose. 



This mode of origin of the larval mines seems to be different from 

 anything described hitherto, and therefore it is difiicult to decide to what 

 group the insect making the mine belonged. In the Museum of Com- 

 parative Zoology at Cambridge is a mine of the European Scolytus rugu- 



