196 Illinois State Laboratory of Natural History 



collar ; lateral grooves distinct. The median portion of the 

 pleune appears finely aciculated, but they are finely sculptured 

 throughout. Scutelluiu bifoveate and more coarsely sculptured 

 than the mesonotum but not wrinkled like the two species just 

 described. Foveae broad and shallow and sculptured at bottom 

 like the rest of the scutellum. Abdomen dark rufous, almost 

 black above, 2d segment occupying somewhat less than half of 

 the dorsum, apical portion of 3d segment feebly punctured, fol- 

 lowing segments, except 7th, more strongly and densely punct- 

 ured, 7th segment covered with a net-work of fine lines but no 

 punctures. Wings hyaline, nervures, except the two transverse, 

 very slender, areolet wanting. Feet, including coxffi, entirely 

 rufous, tibiae of the hind pair in a few cases rather dark. 



Male. — Length, 2.2 mm., 2d abdominal segment occupying 

 half of the dorsum, antennse 14-jointed, last segment once and 

 a half as long as the preceding; otherwise as female. 



Described from numerous bred specimens from alcohol; 

 accessions number 5500. Illinois. 



A. minor n. sp. 



Bred from the same stem of Silphium as the preceding 

 species and about half as numerous. 



Gall-fly. — At first sight the flies of this species appear 

 to be miniatures of A. rufus, but there are structural differences 

 that make it necessary to give them a separate description. 

 They differ from rufus as follows: 



Length of females 2 mm., of males 1^ mm.; collar deeper 

 rufous. The most apparent structural differences are in 

 the mesothorax and scutellum. The parapsidal and median 

 grooves in minor do not appear as sharply defined furrows but 

 only as broad slightly depressed lines with sloping sides. The 

 foveffi of the scutellum are rather deep at base, extend 

 far back, and are not separated by a sharply defined septum but 

 by a broad slightly elevated ridge. The scutellum is also longer 

 in proportion to its breadth and is perceptibly narrowed at the 

 sides, about midway of the length. 



Accessions number, 5500. 



