364 



3. A small projection on outer under side of base of upper protuber- 

 ance Chrysopila. 



— No small projection on outer under side of base of upper protuber- 

 ance Leptis. 



Atherix Meigen 



GENERIC CHARACTERS 



Larva (PI. LII, Fig. 10). — Head small, entirely retractile, inter- 

 nally pyriform. Abdomen with lateral appendages and well-de- 

 veloped paired pseudopods which are armed with curved apical 

 spines, as shown in Figure 10, Plate LII; apical segment ending in 

 2 long protuberances which are fringed with long hairs; 2 rounded 

 blood-gills below base of apical protuberances. 



Pupa. — Unknown to me. 



Imago. — The species differ from those of other Leptidae in pos- 

 sessing the following combination of characters: third antennal joint 

 reniform; basal antennal joint not thickened; arista dorsal; third 

 tibiae with 2 spurs ; front tibiae without apical spurs ; anal cell closed ; 

 discal cell present. 



HABITS OF EARVAE 



The larvae are aquatic, living in flowing streams. 



I have not seen any larvae of this genus from Illinois, the material 

 before me being all from streams in Yellowstone National Park (S. 

 A. Forbes) and from mountain streams in Montana (C. C. Adams). 



HABITS OE IMAGINES 



See under family. 



Symphoromyia Frauenfeld 



I have not seen larvae of this genus, and the characters used in 

 the key are from Beling's published description of a European species. 



Chrysopila Macquart 



GENERIC CHARACTERS 



Larva (PI. LII, Fig. 6). — White. Tapered anteriorly, stout 

 posteriorly, the apical segment ending in 4 stout processes, between 

 the lateral pairs of which is a smaller process (PI. LII, Fig. 11) ; head 

 as in Figure 8. Anterior spiracles small, lateral metathoracic and 



