1924 ] North American Species of Opacifrons and Pteremis 131 
joint. Wings slightly browned; veins brown; costa ending 
beyond third vein, first and second sections black, second section 
three-fifths as long as third; last section of second vein two and 
one-half times as long as basal section of third vein; penultimate 
sections of third and fourth veins subequal and twice the length 
of the outer cross vein; last section of third vein straight and 
ending a little before wing-tip, last section of fourth vein evanes- 
cent and not reaching wing-margin; fifth vein traceable one- 
half way to wing-margin from outer crossvein. Abdomen cy- 
lindrical; second segment of abdomen one and one-fourth 
times as long as third; hypopygium large. Halteres with stem 
and tip of knob yellow. Length: 1 mm. 
Type. — Male, Bovill, Idaho (Melander). 
Paratypes. — Five specimens from the following localities: 
Washington: Sultan, Mt. Constitution, Tacoma, (Melander). 
Idaho: Priest Lake (Melander). 
Pteremis Rondanis. 
Rondani: Prodr. I. 124 (1856)., Coprom. Bull. Soc. Ent. 
Ital. XII 41 (1880). 
Duda: Abhand. zool,-bot. Ges. Wien X. I. 28 (1918). 
Head large, broader than thorax; wings rudimentary; 
costa extending considerably beyond third vein; outer cross vein 
absent; last section of third vein straight or but slightly curved 
up; preapical bristle present; middle tibise with a number of 
minute apical bristles, never with a single strong, apical bristle; 
middle metatarsal bristle absent. 
Genotype. — P. nivalis Haliday. 
Species of Pteremis Rondani. 
1. Wings very short, not reaching beyond the second ab- 
dominal segment; second vein incomplete, not reaching 
costa; face and cheeks piceous, concave in profile; shining 
black species. Fig. 3 parvipennis n. sp. 
Wings longer, reaching the fourth abdominal segment 2 
