132 PROCEEDINGS OF THE NATIONAL MUSEUM. voL, 62, 
with broad, reddish yellow posterior margins; the following segments 
are largely shining reddish yellow, more or less blackish at the bases; 
the pile of the abdomen is light reddish yellow. 
The halteres are pale reddish yellow. The wings are tinged deep 
yellowish, the veins strong, partly, especially on the fork of the third 
vein, blackish. The stigma of the wing is not plain. 
Type locality.—Colorado. 
Type.—In the United States National Museum, Cat. No. 26027. 
REFERENCES TO LITERATURE ON NORTH AMERICAN THEREVIDAE. 
1821. WIEDEMANN, Dipt. exot., pp. 112-114 (two species described from Georgia). 
1823. Say, Journ. Acad. Nat. Sci. Phila., vol. 3, pp. 39-40 (description of Thereva 
nigra). 
1824. Say, Long’s Exped. to St. Peter’s River, vol. 2, Append., p. 370 (description 
of Thereva frontalis). 
1828. WIEDEMANN, Auszereurop. zweifl. Ins., vol. 1, pp. 235-236 (notes on North 
American species). 
1829. Say, Journ. Acad. Nat. Sci. Phila., vol. 6, p. 156 (description of T'hereva albi- 
frons). 
1840. Macaquart, Dipt. exot., vol. 2, pt. 1, pp. 24-26 (description of Thereva rufie 
cornis and T’.. haemorrhotidalis). 
1848. WALKER, List Dipt. Brit. Mus., vol. 1, pp. 221-224 (six species of Thereva are 
described, three really belonging to Psilocephala). 
1852. WALKER, Insecta Saunders., Dipt., vol. 1, p. 197 (description of Tabuda fulvipes). 
1861. BrEwuarp!, Saggio di Ditterol. Messic., vol. 2, pp. 88-92 (four species are de- 
scribed from Mexico). 
1862. Evert, Proc. Ent. Soc. Phila., vol. 1, p. 217 (record of Tabuda fulvipes). 
1867. ScuinER, Reise der Novara, Dipt., pp. 145-146 (remarks on the genera of the 
world and descriptions of several new species, none from North America). 
1869. Loew, Berlin. Ent. Zeitschr., vol. 18, pp. 7-12 (10 North American species 
described). 
1869. Loew, Berlin. Ent. Zeitschr., vol. 13, pp. 166-172 (four North American spe- 
cies described). 
1872. Loew, Berlin. Ent. Zeitschr., vol. 16, p. 74 (new species described). 
1874. Loew, Berlin. Ent. Zeitschr., vol. 18, p. 382 (Thereva hirticeps described). 
1876. Lorw, Zeitschr. f. d. ges. Naturwiss., vol. 47, p. 319 (description of Psilo- 
cephala laevigata, P. platancala, and Thereva melanophleba). 
1877. OstEN SackEN, Bull. U.S. Geol. Surv., vol. 3, p. 274 (description of T. vialis 
and notes on other western species). 
1878. OstEN SacKEN, Cat. Dipt. N. America, ed. 2, pp. 96 and 239 (lists the species 
and gives notes on Walker’s species). 
1886. Wi.iiston, Trans. Amer. Ent. Soc., vol. 13, p. 294 (description of Thereva 
crassicornis). 
1887. OstEN SackEn, Biol. Centr. Amer. Dipt., vol. 1, p. 162 (description of 7’. bol- 
bocera and a list of the previously described species from Mexico). 
1889. Bigot, Ann. Ent. Soc. France, ser. 6, vol. 9, p. 321 (description of Ozodicer- 
omyia mexicana). 
1893. CoquILLett, Can. Ent., vol. 25, pp. 197-201 (a synopsis of the genus Thereva 
with a table of species and descriptions of five new species). 
1893. CoquiLuetr, Can. Ent., vol. 25, pp. 222-229 (a synopsis of the genus Psilo- 
cephala with a table of species and descriptions of five new forms). 
