5 
fore seems evident that the egg is laid on or in the slight flow of resin 
that exudes from such a wound (fig. 8,7). No evidence was found that 
the larva could make an independent entrance through the bark. 
DESCRIPTION OF THE STAGES. 
The larva.—The larva (fig. 4, 7) is a whitish maggot with a small, 
wrinkled head almost buried in the front end of a plump, subcylindrical, 
segmented body that terminates behind in a long, telescopic, protractile 
tail. The head (fig. 4,w) has a pair of stout, black, forked mandibular 
hooks, and is densely clothed with short brown spines. When exam- 
ined with a microscope, a pair of small branched feelers (antennze) are 
found just above the hooks. The body seems smooth to the naked eye, 
but it is quite thickly covered with minute spines. Just back of the 
head, upon the dorsal surface of the first segment, is a pair of widely 
separated, small, fleshy tubercles. Each bears a dark brown breathing 
organ (spiracle). Most of the segments have a pair of fleshy append- 
ages, probably false feet, on their ventral surface. Upon the ventral 
surtace of the last segment, and surrounding the anus, which opens there, 
are often seen five -or six heavily convoluted, bladder-like protrusions. 
These are probably the rectal glands. 
The tail is about the same length as the body. It bears several pairs 
of the fleshy foot-like organs, and terminates in a dark-brown fork, each 
branch of which is armed with a whorl of four strong plumose bristles. 
It is simply a long breathing tube that may be lengthened or shortened 
at will to meet the varying depth of the resin mass covering the body. 
The tip, or fork, bears and protects the spiracles, which must always 
be kept out to the air. The full-grown larva, including tail, is from 
0.6 to 0.8 inch in length, and 0.08 to 0.12 inch in width at its largest 
part. 
The puparium.—The puparium (fig. 4, s, ¢) is formed within the last 
larval skin. The larva lies doubled up with the tail bent over the back 
and the head just within the outer surface of the resin mass. The tail 
shortens up, appears to lose its breathing function, and the body 
becomes more compact and solid. The two spiracle-bearing tubercles 
on the back of the first segment become elongated into horns, and form 
the breathing tubes. The Jarval skin does not seem to become very 
much thickened. nor any darker, as is usually the case in related forms. 
It remains quite transparent and the outlines of the puparium can be seen 
through it quite plainly. The puparium, including the inclosing larval 
skin, is 0.28 to 0.36 inch in length, and 0.12 to 0.16 inch in width. 
The adult. —When full development is reached, the head of the larval 
skin is pushed out and the adult emerges. This usually takes place 
in April or May. The adult (fig. 4, w) is a small black fly, about 0.36 
inch in length, 0.12 inch in width, with wings 0.52 inch in length, and 
is rather densely covered by medium black hairs. The male is more 
