1916.] NATURAL SCIENCES OF PHILADELPHIA. 511 



A Key to the Near ctic Species of Gonomyia. 



1. Two branches of the radial sector attain the wing-margin 



(Subgenus Leiponeura Skuse.) 2 

 Three branches of the radial sector attain the wing-margin 7 



2. Outer deflection of M 3 absent, the cell 1st M 2 being open 3 



Outer deflection of M 3 present, the cell 1st M 2 being closed 4 



3. Costa conspicuously china-white; legs banded with white; male 



hypopygiuni with the dorsal pleural appendage triangular, 

 the caudal angle a prominent elongate spine; ventral pleural 

 appendage a flattened blade whose inner caudal margin is 

 armed with about five or six acute chitinized appressed teeth, 

 of which the innermost is the largest. (Eastern United 



States.) alexanderi Johnson. 



Costa not conspicuously china-white; legs without white bands; 

 male hypopygium with the dorsal pleural appendage broadly 

 triangular, the caudal angle a short spine; ventral pleural 

 appendage a flattened blade bearing near its dorsal inner side 

 a sharp chitinized point; no serrations along the lobe. 

 (Western United States.) cinerea Doane. 



4. Pleural stripes conspicuous; stigma distinct 5 



Pleural stripes indistinct or feebly indicated; stigma lacking or 



very faint 6 



5. Legs with the femora tipped with dark brow r n; costal margin of 



the wings conspicuously light yellow, the stigma pale browm. 



(Northeastern United States.) sacandaga Alexander. 



Legs with the femora indistinctly darkened at the tip; costal 

 margin of the wings not yellow, the stigma dark browTi. 



(Southeastern United States and southward.) 



pleuralis Williston. 



6. Pleura plumbeous with a pale yellow stripe; male hypopygium 



with the pleural appendage armed with a strongly curved 



hook. (Southeastern United States and southward.) 



pner Alexander. 



Pleura unstriped, pale; male hypopygium with the pleural 



appendage very elongate, slender, decussate in a position of 



rest, the inner face at the apex with a strong bristle. (Eastern 



Lmited States.) manca Osten Sacken. 



7. Radial cross-vein present (subgenus Gonomyella Alexander) 



i Southeastern United States and southward.) 



slossonce Alexander. 

 Radial cross-vein lacking (subgenus Gonomyia Meigen) 8 



8. Basal deflection of Cu x far before the fork of M ; subcosta long, 



ending beyond the origin of Rs 9 



Basal deflection of Cui at or beyond the fork of M; subcosta 

 short, ending opposite or far before the origin of Rs 11 



9. Wings clear. (Northeastern United States.) 



mathesoni Alexander. 

 Wings spotted 10 



