14 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. CO. 



11. TACHYTRECHUS AURATUS Aldiich. 

 Fig. 8. 

 Macellocerus auratus Aldrich, Trans. Amer. Eut. Soc, 1896, vol. 23, p. 83. 



Male. — Face slightly longer than height of eye, just below the an- 

 tennae nearly half as wide as at the lower end, golden yellow, with- 

 out luster; front very deep metallic-green dusted with brown, dull. 

 Antennae bright yellow, third joint slightly infuscated with brown ; 

 first joint nearly three times as long as the second and third, black 

 bristly hairs on upper side, second and third joints quite small. 

 Arista very long, about one and one-half times the height of the head, 

 lamella brownish-black and very large, with a very small white area 

 at the base. Orbital cilia black above, yellowish-white below. Thorax 

 and abdomen bronze-green, in some lights somewhat obscured by a 

 greenish- white pollen dark and more shiny along the apical edges. 

 On each side of thorax, in front of the wings, there are two velvety 

 black spots. Hypopj'^gium large, pubescent, which is denser and 

 yellowish- white at the base, towards the apex with a decided purple 

 luster; lamella very pale yellowish, somewhat triangular, hairs and 

 cilia black. Front coxae pale yellow, infuscated at extreme base, 

 with a silvery dust on front surface ; middle and hind coxae brownish 

 black, reddish-yellow at the apex. Middle coxae with a golden pollen 

 on front surface, hind pair lightly dusted with a whitish pollen. 

 Legs mostly yellow, tips of middle and hind tibiae and all the tarsi 

 except the base of the front metatarsus (which is yellow) infuscated 

 with brownish-black. In certain lights the front tarsi and under sur- 

 face of the middle and hind femora silvery white. Front femora 

 with long curly hairs on the outside ; middle and hind femora with 

 large bristly hairs on the underside on the apical half. Wings hya- 

 line. Halteres reddish-yellow, slightly infuscated at base of stem. 

 Tegulae pale yellow with long black fringe. 



Female. — Face wider and silvery-white. Front deep metallic- 

 green. Antennae very short, third joint a little larger, mostly brown- 

 ish-black, yellow along the lower edge. Arista not quite as long as 

 face, no lamella, somewhat of an angle near the base; penultimate 

 joint about four times as long as wide. Legs more reddish, tips of 

 all tibiae and tarsi blackish. Under side of femora, all tibiae and 

 tarsi with sih-ery dust. Otherwise like the male. 



Length, 5 mm. 



Type locality. — Moscow, Idaho, June 18, J. M. Aldrich, collector. 



Distribution. — Juliaetta, Idaho; Boulder, Colorado; Alum Eock 

 Park, San Jose, California, April 5, 1906 ; Highland Springs, Cali- 

 fornia, August 9, 1911; Mount Lowe, California, July 4, 1917; origi- 

 nally described from one male and two females. Two cotypes (Cat. 



