140 
LETTEES FEOM ALABAMA. 
The egg is laid by the parent moth, on or beneath 
the bark of a living tree. The larva, as soon as 
hatched, eats its narrow passage into the heart, 
living on the particles of wood which it abrades. 
Of course its ejecta fill up the cell behind as fast as 
it proceeds, and thus it has no alternative but to 
go forward. Indeed, were it not so, it could not 
retrace its steps ; for the diameter of the chamber 
is always but just sufficient for it to move com- 
fortably in ; and as it increases in size, it of course 
makes a wider passage ; therefore, the excavation 
which contained it yesterday, would to-day be too 
straight to admit it. 
This species appears to be slower of growth 
than most caterpillars, taking two or three years 
to attain its full size. Before it goes into the 
pupa state, it either opens the passage into the 
air or (which I think more probable) leaves an 
extremely slight lamina of wood unpierced at the 
very extremity, which the pupa can break with its 
head, or perhaps dissolve with some secreted fluid. 
From my finding the pupa in the heart of the tree, 
I presume that it waits until the time of exclusion 
of the perfected moth is near, before it comes to 
the edge ; then works its way outward by means 
of a ring of little points directed backward, with 
which each segment of the body is furnished. On 
its arrival at the mouth, which appears (at least in 
all the cases I observed) to take place during the 
night, it projects the fore-parts until half of the 
insect is exposed; then the skin opens at the usual 
places, and the moth is evolved, leaving the empty 
puparium sticking in the hole. 
I took the caterpillar home, and put him into a 
box, with some pieces of the wood of the tree ; 
