COLEOPTERA— SCOLYTID^. 469 



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

 some other rare cases, the young- larvae do not begin to mine at right angles 

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

 ing chamber or the extremity of one of the main galleries, and thence burrow 

 in irregular and somewhat interlacing mines in a longitudinal direction (see 

 Fig. 24), 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 millimeter 

 and they vary greatly in depth. The depth of those at a may be seen in 

 the enlarged drawing of this portion in Fig. 25. 



The connection between the main gallery and the mines is often ob- 

 scure, owing doubtless to the younger larvje burrowing more in the bark 

 than in the wood (the bark being here entirely lost). In one case (c) 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 oviposition. 



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

 thing hitherto described, and it is therefore difficult to decide to what minor 

 group of insects the creature constructing the mines belonged, In the Museum 

 of Comparative Zoology at Cambridge is a mine of Scolytus rugulosus on 

 cherry, which shows a somewhat similar distribution of the larval mines, 

 emerging and diverging from one point of the mating chamber ; but the 

 main galleries are reduced to almost nothing, and the figures of the mines 

 of this species given by Ratzeburg are altogether different. 



This specimen is one of those branches " of some coniferous tree," which 

 Mr. liinde in his article on the glacial and interglacial strata of Scarboro 

 Heights,' states to occur in the layers between the beds of clay and sand 

 found between his " till No. 1 " and " till No 2," and which are described 

 as "flattened by pressure, their edges . . . worn as if they had been 

 long macerated in water." This is exactly true of the present fragment. 



I Cau. Jour. Sc. Lit. Hist., XV, 388-413, plate, 1877. 



