DIPTEROUS LEAF-GALLS ON OAK. 207 



well-developed gall two larvae, the two cells sometimes separated, but more gener- 

 ally niuning into one. The larva is of the usual orange color, but appears to be 

 somewhat shorter and thicker than those I have before noticed. Length, when not 

 crawling, .14 of an inch. Head quite pointed, and the first few segments doubly- 

 wrinkled. Two appendages at head, and two brown spots near it superiorly. Breast- 

 bone brown and clove-shaped. Terminal segment with two acute prominences. 



October 29, 1869. Upon opening several galls to-day, I found one which contained 

 four larvse, two in each cell. 



January 1, 1870. Many of the larvse are on top of the ground, though most of them 

 are yet in the galls. Some of the galls have become softer, and have peeled open ; 

 and it is from these, I think, that the larvse have escaped. 



April 3. I examined them to-day and find that, though some of them are empty, the 

 great majority of them contain either pupse or larvte. The larva works and loosens 

 a passage, pushing the debris to the surface. It then lines its cell with a delicate 

 silken lining, and transforms to a pupa of the exact color of the larva ; the head being 

 furnished behind the antennje with two thorns ; the wing-sheaths reaching to the 

 third abdominal joint, and the hind legs, which are free from the body, to the fifth. 



Many of the galls contain a white parasitic maggot with a conspicuous black pointed 

 head, divided longitudinally with a lighter line and with two brown spots behind it. 



May 2, 1870. Many of the flies have issued, but all so far seem to be females. The 

 antennae are 14-jointed (double jointed -f 12) and are scarcely at all verticillate, and 

 only the slightest restriction on basal one; no pedicels; length of joints very grad- 

 ually decreasing from 3 to 14. Nervules of wings as in true Cecidomyia. On opening 

 many galls to-day I find most of the larvai within cells. A great number of parasites 

 have issued within the past few days, and on opening the galls I find the perfect para- 

 site within a cell between two others occupied by Cecidomyia larvae. So many of 

 the galls are empty, that I greatly incline to believe some of the larvae left them 

 and entered the ground, the more so that the pupal integuments were all ou the 

 ground. 



July 22, 1870. Larva just hatched and barely visible. Gall itself fully formed and 

 golden yellow. (MSS. notes. Also see Amer. Ent., Vol. II, p. 29.) 



289. Cecidomyia qnercus-majalis Osten Sacken. 



Blister-lite gall of Cecidomyia on youDg leaves of the pinoak 

 { QuercKS ^alustris). Generally these galls occur on the principal rib& 

 of the leaf; sometimes between the ribs. They are oblong, blister-like, 

 the hollow surface somewhat uneven, wrinkled, walls thin ; color pale 

 green or reddish. They bulge out on one side of the leaf and have a 

 longitudinal slit on the other. Galls projecting on the under side of 

 the leaf aud having the slit on the upper side seem to be somewhat 

 more common than those of the opposite description. The slit can be 

 opened without injuring the gall by geutly pulling at the sides. Such 

 galls which grow upon a rib show a trace of it on their longitudinal 

 diameter. The larva, which can be taken out of the slit without lacer- 

 ating the gall, is rather larger than the majority of the larvse of Ceci- 

 domyia (about 0.2 of an inch long), and not reddish, as usual, but white, 

 smoorh ; the breast-bone is hardly visible, as its front part only is horny, 

 having the aiipearance of a transverse, reddish-brown wavy line. The 

 last abdominal segment has several minute, fleshy, pointed projections. 

 The larva drops to the ground through the slit at a certain period of its 

 development; hence, empty galls are often found. Found in consid- 



