THE CANADIAN ENTOMOLOGIST 321 



face of the posterior coxa^. Halteres very long and slender, pale. 

 Legs with the coxae yellow marked with brown as described above; 

 trochanters brownish yellow; femora brown, slightly paler at the 

 extreme base; tibiae and tarsi dark brown. Wings with a strong 

 grayish brown tinge; stigma pale brown; veins dark brown; vena- 

 tion: Sc rather long, ending slightly beyond the origin of Rs; Rs 

 very long, longer than Ri+s; basal deflection of 7?4+5 very short 

 or lacking; r-m very long, arcuated. 



Abdominal tergites dark brown, the extreme lateral margins 

 and the parts of the hypopygium largely yellowish; sternites 

 light brown, the caudal margin very broadly ringed with yellow. 

 Hypopygium with the pleurites moderately long, the dorsal angle 

 produced caudad and slighth' dorsad as an elongated fleshy lobe 

 that is sparsely hair^', the hairs on the outer face strong, those 

 on the inner face weak; dorsal pleural appendage a short, fleshy 

 lobe whose caudal margin is produced into a powerful, curved, 

 heavily chitinized hook, directed inward and dorsad; at the tip 

 of the fleshy portion of the lobe are two stout hairs and a group 

 of about eight smaller ones: ventral pleural appendage very long, 

 slender, beyond the base slightly expanded, the apical portion 

 slender, slightly expanded toward the tip, dusky in colour and pro- 

 vided with an abundance of long, delicate hairs. Penis-guard 

 pale in colour, simple, slender from an enlarged base, the apex 

 split by a deep, rounded notch. 



Habitat — Rocky Mountain Region. 



Iljlo'ypr — cf, Webster, Co'orado, near Platta Ctnrn; Au^u.-t 

 24-26, 1915; altitude 9,500 feet (E.* J. Oslar). 



Allotype — 9 , topotypic. 



Paratypes — 30 cf 9 , topotypic. 



The types are in the collection of the author. 



Belongs to the subcinerea group; a long-winged, dark-winged 

 fly with exceedingly elongate halteres. In some specimens the 

 pale colour on the sides of the mesonotal pra^scutum is obscured 

 by the gray-brown of the dorsum. 



Gonomyia (Gonomyia) mexicana, sp.n. 



Male — Length 6.1 mm.; wing 6.8 mm. 

 Female — Length 7 mm. 



