390 ENTOMOLOGICAL SOCIETY 



cause the flow of resin. They probably breed in such exudations 

 as arise from various injuries to the tree, caused by insects, birds, 

 or other agencies. 



NOTES ON CERTAIN CECIDOMYIIDOUS GALLS ON CORNUS. 

 By C. H. TYLER TOWNSEND. 



On November 23, 1890, in company with Mr. Schwarz, I 

 found at Vienna, Virginia, a large number of ceciclomyiidous 

 galls on the ends of terminal twigs of Cornus. probably Cornus 

 florida. Some of the galls are short and oval, while others are 

 very much elongated. They are all reddish in color. Inside of 

 some," which were opened, were found orange-colored larvae of 

 different sizes, one in each gall. Some of the galls containing 

 these larvae had exit holes in them. In one of the latter galls 

 was found a white hymenopterous larva, doubtless that of a para 

 site. These galls were exceedingly abundant on every sprout, 

 shrub, and small tree of Cornus which was to be seen, in most 

 cases every terminal twig on the bush having been stung, so 

 that these gall-gnats must be very injurious to the tree. On one 

 large tree were noticed a number of terminal twigs not stung, 

 which in place of galls bore the next year's flower-buds. It 

 therefore seems that this midge stings the very spot which should 

 produce a flower-bud, thus in some cases entirely depriving a tree 

 of its flowers. 



There may be two species concerned in the formation of these 

 galls, the elongate gall being the work of one species, and the 

 short, oval one that of the other. It may be interesting to note, in 

 passing, that a large larva from one of these galls was noticed to 

 be still very active after an immersion of one or two hours in 

 alcohol. 



The galls themselves are either swellings of the terminal bud 

 and twig together, or elongated swellings of the twig before its 

 terminus. In either case the inhabitants live in the centre, in the 

 pith of the stem. This, therefore, is rather a rudimentary and 

 primitive gall. In almost every case each gall had at this date an 

 exit hole, even those which contained cecidomyiid larvae as above 

 noted. A double handful were collected and taken home. 



On the next day some of the galls taken home were opened, 

 and several larvae were found in the elongate as well as in the 

 short galls. Three larvae were found in one gall. The exit holes 

 in the greater number of the galls are those doubtless of some of 

 the larvae which had already emerged to go into the ground, if 

 such be their habit, and not those from which any parasite had 

 escaped. 



On the 5th of December nearly all of the remaining galls were 

 opened to determine the number of larvae still left within them. 



