THE CANADIAN ENTOMOLOGIST, 77 



before the leaves appeared. The white, thin-walled larval cells are im- 

 bedded in woody tissue from which it is almost impossible to detach them. 

 The galls formed around the lateral buds are from one-half to three- 

 fourths of an inch in diameter, but those around the cluster of terminal 

 buds are often an inch in diameter, and instead of a single branch, several 

 are often found growing out of a single gall. They do not seem to affect 

 the growth of the branches the first year, but must seriously injure the 

 tree the following year when the perforated galls begin to decay. This 

 species was very common last year in a thicket which I have searched for 

 galls every season for the last fifteen years without discovering it. The 

 flies are of both sexes and they leave the galls in July. 



The flies, of which 1 have many thousands, may be described as 

 follows : 



Female : Head clear yellowish brown ; the vertex when highly magni- 

 fied shows a finely crackled surface. Eyes and ocelli black, the latter 

 very near together. Face rounded and full, with a few short hairs scat- 

 tered over it, and a brush of long bristly hairs on the mentum. Tips of 

 the mandibles show a faint duskiness. Antennae 13-jointed, ist joint 

 club-shaped, abruptly truncate ; 2nd small, regularly ovate ; 3rd and 4th 

 slender, 3rd a trifle shorter than the two preceding taken together, 4th 

 equals the ist in length. The first four joints are of a uniform clear yel- 

 lowish brown, while the remaining ones are of a dull dusky brown ; the 

 transition from one shade to the other is abrupt, and not gradual as in 

 most species. The remaining joints are also considerably larger than the 

 third and fourth, and are short and sub-equal, except the last, which is one 

 and a half times the length of the preceding. Thorax dark brown, semi- 

 translucent, the scutellum and post-scutellum almost black. Mesothorax 

 smooth and shining, but highly magnified it appears very finely rugose. 

 Parapsidal grooves absent, scutellum darker and more strongly rugose 

 than the mesothorax. Fovse wanting. Two anterior pair of legs pale 

 yellowish brown, posterior pair much darker. Wings hyaline. The ist 

 and 2nd transverse and the subcostal veins rather heavy, and a dark 

 smoky brown. The cubitus disappears about midway between the two 

 transverse veins. Abdomen smooth and shining and apparently black. 

 The first segment one-third longer than the very long second segment, 

 remaining segments short. 



Length, body .09, wing .09, antennae .06. 



Male : Entire body a few shades darker than the female. The legs a 



