194 DIPTERA OF NORTH AMERICA. 



the leaf. The presence of the larva is indicated on the other side 

 of the leaf by a round yellow spot. The structure of the larva is 

 peculiar : it has rows of fleshy, pointed tubercles along its back, 

 like the larva of C. pini inopis (described below), with which it 

 agrees in some respects in its habit of fastening itself to the sur- 

 face of the leaf by means of a viscous substance. 



9. G. solidaginis Lw. Gall on Solidago produced by the arrest 

 of the growth of the stalk, which causes the leaves to accumulate 

 round the same spot and thus to produce a large imbricated de- 

 formation. It begins to appear already in July, but the flies 

 escape only late in the fall. The following description of gall and 

 fly have been prepared by Mr. Loew : — 



11 The gall (Tab. I, fig. 8) represents a globular head of the size 

 of 1 ^ to 2 inches formed by hundreds of leaves, the exterior ones 

 being only little altered, the interior ones becoming more and 

 more narrow ; on a closer examination we easily perceive that this 

 structure results from the coalescence of several deformations at 

 the tips, of abortive twigs; in a specimen which I dissected I 

 counted five such shortened twigs. At the top of each twig there 

 is a single gall, without compartment, somewhat of the shape of a 

 very small seed, and having in its interior a cavity widened a little 

 underneath. The tip of one of them (Tab. I, fig. 10) showed at 

 its end three small convergent lobes, giving it the appearance of 

 being produced by three coalescent leaves.* I could not discover 

 this structure in the others ; I found only a rounded, rather irre- 

 gular opening at the tip. The insect which produces this defor- 

 mation likewise belongs to the genus Cecidomyia in the restricted 

 sense. 



C. solidaginis Loew. % and 9. (Tab. I, fig. 4— 7.)— Fusca, ab- 

 domine fasciis rufis et nigris picto ; antennarum flagellum in mare arti- 

 culis 20 vel 21, in fcemina circiter 18; aire pilosre, nigricantes, venula 

 transversa nulla ; terebra focniinre inodice elongata. 



Fuscous, abdomen with black and red bands ; flagellum of the antenna? 

 with 20 or 21 joints in the male, with about 18 in the female; wings 

 hairy, blackish, without transverse veinlet; borer of the female mode- 

 rately long. Long. corp. % 0.16, 9 0.17. Long. al. % and 9 O.lti — 

 0.17. 



Thorax with the pleura? sometimes brown, sometimes dark fus- 

 cous, with black hairs. Abdomen of the female with distinct 



