5 



fore seems evident that the egg is laid on or in the slight flow of resin 

 that exudes from such a wound (fig. 3, f) . 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, r) 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 (antennae) 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 browp breathing 

 organ (spiracle). Most of the segments have a pair of fleshy append- 

 ages, probably false feet, on their ventral surface. Upon the ventral 

 surface 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, t) 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 larval 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 m 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. Th^ adult (fig. 4, u) is a small black fly, about 0.36 

 inch in length, 0.12 inch in width, with wings 0.32 inch in length, and 

 is rather densely covered by medium black hairs. The male is more 



