22 
feeder. Soon ifc bores into the bark and forms a small chamber 
beneath the outer pellicle, which is raised like a blister. Gradually 
this is enlarged, and there the larva lies snugly curled up, and so 
passes its first winter. Considerable activity is shown the next spring, 
and frass is freely extruded, though the bark still remains raised, 
even when the chamber is extended down to the wood. By the 
middle of April, about half the larvae have bored a small hole into the 
solid wood ; others are much more backward, and may still be found 
in the outer layer of bark as late as the last week in May or the 
beginning of June. The hole is first bored horizontally towards the 
centre of the stem, then vertically, usually in an upward direction. 
The passage is gradually enlarged and always kept of the same 
calibre throughout. The larva is enabled to do this by its extraordinary 
power of turning in a narrow space. 
In the autumn most larvae complete their tunnels and make a 
cocoon ready for emergence the next June or July, but some of the 
more slowly growing ones pass yet another year in the larval state, as 
is proved by one which I found in April and kept through the winter. 
Instead of pupating it lived on, still quite small, past the time of 
emergence of the moth, and would have no doubt produced an imago 
the next summer, after passing two whole years and part of two others 
as a larva. 
The completed gallery runs upwards or downwards, rarely the 
latter. I have notes of nine, of which three produced imagines and 
six parasites, for a distance varying from three quarters of an inch to 
three inches—usually about two and three-quarter inches. The blind 
end is pa.cked with frass for about a quarter of an inch ; next comes the 
thin cocoon made of silk and frass, then the smooth passage running 
at first parallel with the long axis of the stem, then curving almost at 
a right-angle out to the exit hole. The tunnel is always carried down 
beyond the curve, sometimes as much as a quarter of an inch, but the 
prolongation is filled with frass and the surface towards the tunnel 
made quite smooth. Across the part where the tunnel leaves the 
wood is a curtain of silk and frass. External to this is the old larval 
chamber varying in size and shape and partly filled with frass, and 
finally in the most perfect dwellings the cap. This is formed in the 
autumn and is a round or oval piece of bark, 5 to 13 mm. in diameter, 
cut out by the larva from within and kept in place by silk, or silk and 
frass. In many it fits the hole in the bark perfectly, in others there 
is a very obvious ring of frass and silk filling the gap, showing that 
some bark has been eaten away, and that the cap is not merely formed 
by the drying and shrinking of the undermined bark. This is also 
shown'by a stick, in which the cap is formed of two separate bits of 
bark, united to one another and the rest of the bark by frass and silk. 
In other cases there is a ring of small boles in the bark, each filled 
with frass; in these the formation of the cap has been started and left 
incompleted. In some, the caps fall off, and in others, the larva goes 
a stage further and eats the bark, which should have formed it 
leaving a mass of loosely bound frass in its place. The proportion of 
perfect caps to the total number is small, I counted 20 out of 100 on 
one occasion, but a much larger proportion of imagines is produced 
from these than from the others. Variations in other directions from 
xix. 
