FAMILY CERAMBYCIDAE 309 



in it eats a tunnel down into the heart of the tree. The tunnel 

 so made may be carried more or less horizontally, or may go m at 

 an angle; it is 3 in. to 5 m. in length, being much broader than the 

 diameter of the grub constructing it, and the latter can easily turn round 

 in it (see fig 211). The winter is spent in eating out this tunnel, and 

 the larva thereby escapes the cold which it would feel in severe seasons 

 if it remained just beneath the bark in its gallery in the sapwood. 1 his 

 accounts for the at first inexplicable fact that the great cold experienced 

 in Ouetta during the winter does not apparently in any way affect the 

 number of beetles issuing from the trees in the spring, even after very 

 severe winters. As spring approaches, the larva commences to carry 

 this tunnel in the wood in the direction opposite to that in which it 

 originallv proceeded, and the portion of the tunnel now eaten out is the 

 pupaf chamber. This is some three inches in length, and may be 

 completed bv about the end of May (see fig. 211). A number of full- 

 grown larvae at rest m this chamber and just about to pupate were 

 taken on the last day of this month. It was noted that these larvae varied 

 greatly in size, but this has no significance, since the beetles themselves 

 vary very greatly in size. This difference in size may be due to a certain 

 extent to the degree of hardness of the wood of the tree in which the 

 o-rub is living. It was noted, for instance, that the galleries in elm were ot 

 smaller dimensions than those usually found in the white poplar, these 

 latter being invariably large. The size of the tunnel in the wood itself wil 

 also of course vary with that of the larva, but from the commencemen 

 where it leaves the sapwood gallery down to the turn into the pupal 

 chamber it is always of considerable width, so broad that the larva can 

 turn round in it. "its length, however, may be but little more than that 



of the grub itself. . 1 ^ 



It will be seen from the above that the larva takes from twelve to 

 fourteen months to reach its full growth after leaving the egg. 



The Pupation of the Larva.-The larva pupates in the long axis of the 

 tree and the pupal chamber appears to be invariably bored out in a 

 direction contrary to that in which the larva was lying at the time it com- 

 menced this work. This chamber is always straight or but slightly curved, 

 and comparatively narrow when compared with the rest of the gallery in 

 the wood above it. Having prepared the chamber, it plugs the top with a 

 mass of gnawed wood, and lines the sides at times, if not always, with a 

 papery lining of a brownish fibrous material. If it has not previously done 

 so it now backs out of the chamber into the broader tunnel above, turns 

 round in this, and proceeds backwards down into the chamber again and 

 builds across the top of the latter a thick white wall of some calcareous 

 substance, lining the sides of the chamber with the same material for a 

 short way down. This wall effectually blocks up the chamber and prevents 

 the entrance of enemies, who would be able to attack and feed upon the 

 helpless insect whilst in its quiescent or pupal state. The time of pupation 



