194 Illinois State Laboratory of Natural History 



the last joint of the antennae as long as the two preceding 

 joints. 



Described from 60 bred specimens bearing accessions num- 

 bers 1928, 5206, 15605, and 15665, all from Illinois. 



The flies live over winter in the galls and emerge from 

 them during the months of May and June of the following 

 year. 



A. laciniatus n. sp. 



Galls. — Individual galls are egg-shaped, from 4 to 5 mm. 

 in length, and occur in clusters on the receptacles of the flowers 

 of Silphium laciniatum. (Plate IX., Fig. 8.) Mr. C. A. Hart 

 has collected a number of these gall-clusters and in description 

 of them says : " They always occur in well-ripened, healthy- 

 looking flower heads, but do not show until the weather has 

 removed the uuinfested flowerets. They are always produced 

 in the sterile flowers of the disk, towards the center." 



Gall-fly. — Female. — Head and thorax opaque black, 

 abdomen shining rufo-piceous, antenniie black; length, 3 mm. 



Head: face between eyes and mouth rather coarsely acicu- 

 late, median ridge with a few coarse punctures or pits, entire 

 surface of head finely and densely sculptured, as in the preced- 

 ing species, middle ocellus at the upper extremity of a broad 

 furrow extending up from the antenna?, the two outer ocelli on 

 the summit of the vertex, mandibles rufous on median portion. 

 Antennae black, 13-jointed, joints 8 and 4 equal, last joint al- 

 most as long as the two preceding; length, 2.3 mm. Thorax^ 

 including scutellum, as in the preceding species. Abdomen 

 rufo-piceous, polished, rather globose, 2d segment occupying 

 scarcely more than one third of the dorsum, 8d segment broad, 

 3d and succeeding segments densely punctured. Wings hyaline, 

 pubescent, nervures very light, areolet wanting. Feet, includ- 

 ing coxae, black; tip of femora, tarsi, and anterior tibia^ rufous. 



Male. — Length, 2 mm.; antennae 14 jointed, as long as the 

 body ; abdomen black, 2d segment occuj>ying fully one half of 

 the dorsum ; otherwise as the female. 



This species is easily distinguished from A. siJphii by the 

 black anteanse, which are 13-jointed in the female, by its much 



