10 PEOCEEDINGS OF THE NATIONAL MUSEUM vol.69 



D^ Fourth tergite shining bronze; wings nearly hyaline; third joint 



narrower than front across ocelli ; 8 mm mamillata Loew. 



C^ Frontal aspect of face partly yellow. 



D\ Hind femur reddish at base ; front unusually long and narrow. 



albistylum Macquart. 



D^ Hind femur entirely black ; front not unusually long and narrow 



(sometimes 8 mm., usually 10-12) quadrata (Say). 



TROPIDIA INCANA Townsend 



Described from Fort Collins, Colorado. Specimens at hand: 2 

 males, 2 females, Florissant, Colorado, June 24, 1907 (S. A. 

 Rohwer). 



Tyfe. — Location unknown. 



TROPIDIA MONTANA Hunter 



Type locality, — Moscow, Idaho. Has been taken subsequently, 

 same locality, April 30-May 17 (J. M, Aldrich). 

 Type. — University of Nebraska. 



TROPIDIA COLORADENSIS (Bigot) 



Xylota coloradensls Bigot, Ann. Soc. Ent. France, ser. 6. vol. 3, 1883, p. 544. 



Very closely allied to T. tnontana Hunter. Described from Colo- 

 rado. Not since recorded. 

 Type. — In British Museum. 



TROPIDIA PYGMAEA, new species 



Male. — Unusually small, dark species with yellow abdominal 

 markings. Ocellar triangle black with rather short, sparse pile; 

 frontal triangle and face black with white pollinosity; antennae 

 small, first two joints dark brown, third yellowish brown; arista 

 about length of antenna, brown; face very prominent, with rather 

 gentle slopes, keel not sharp, straight from antennae to oral margin. 

 Thorax entirely shining black, mesonotum with very short, light 

 pile ; legs black except extreme apices of femora and bases of tibiae ; 

 legs slender hind femur although swollen is less so than any of its 

 congeners; abdomen black, second and third tergites with large yel- 

 low markings extending over the sides; hind margin of fourth 

 tergite yellow; wings slightly smoky; squamae white; halterers 

 faintly yellow. Length 4.5 mm. ; wing 3.75 mm. 



Holotype, male. Soldiers Summit, 7,454 feet, Utah, July 6, (J. M. 

 Aldrich). 



Type.—C^t. No. 27311, U.S.N.M. 



The unusual size, the very short thoracic pile, slender tarsi and 

 abdominal markings easily identify this species. 



