196 Rev. G. A. Crawshay on the 
surface flakes of young bark, which it excavates superficially, not 
burrowing down at once into the inner and wettest bast, where it 
would be suffocated, except in the case of a dying tree containing 
little sap. It first moults two or three times and attains some size. 
In the case of trees recently felled, and healthy at the time of felling, 
I have not known the young larva penetrate entirely the inner bark 
and reach the surface of the wood-cylinder (Plate XV, fig. A.A.A.) 
under three weeks. It will then be found, for the rest of its life, 
feeding on this wettest part of the tree, consuming the soft bast, the 
cambium layer, and sometimes grazing superficially the youngest 
sapwood (Plate XV), though never excavating this as deeply or 
as clean as Callidiwm, L. 
As it excavates it keeps its burrow clear, for a short distance in 
front, throwing back the rejected bitten wood-fibre and ramming it, 
together with the excrementa mingled, into a solid cake with which 
it fills up the entire burrow behind it as it advances. It allows 
very little bitten fibre to accumulate at a time in front, but is 
continually cleaning up. 
For some time prior to, and especially during the excavation 
of the pupa-cavities in the bark a curious ticking sound 
proceeds from the tree, caused doubtless by the action of the 
mandibles, faint at first, but later becoming clearly audible at a 
distance of 15-20 paces on a calm day, when the larva is excavating 
dead bark immediately under the surface of the outer plates. 
I have detected the presence of larve in a standing tree by this 
sound alone early in August 1906. In a small tree where the 
brood is very numerous the ticking procéeds from the whole surface 
of the infected bark continuously. It is a double and sometimes a 
treble tick. As to the cause of this, it may be that the mandibles, 
having passed through the particle of dead bark which the larva is 
biting away, the resistance suddenly removed, meet with a snap, 
overlap, and, in overlapping, the margin of the innermost mandible 
passes across one or more of the ridges on the inner surface of the 
overlapping one, thus causing another “tick” or two to be heard. 
When the larva is feeding in the soft bast I observe no ticking 
sound but rather a squashy sound, from which I infer that it is only 
the greater force needed to bite through the more dead and dry bark 
of the outer plates which gives rise to the sound in question. 
Some pupate in the bark, while others prefer the wood, In the 
latter case, the larva, having bitten the surface of the wood heavily 
for a short distance, enters it suddenly by an elliptical hole, the 
ellipse lying perpendicularly to the circumference of the tree (Plate 
XV, B.z.). Ihave observed but few exceptions to this rule of the 
vertical ellipse in some thousands of holes examined. In these the 
