316 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



but stop ouly a, short distance before the scutelliim. In the female, 

 the three flattened bristles on the hind tibiae do not exist, and the costa 

 is only imperceptibly incrassate. 



2. Tachytrechus sanus u. sp. — Male. — First antenna! joint rather 

 large, reddish-yellow, beset with black hairs on the upper side, especially 

 long toward the tip ; second joint small, placed on the under side of a pro- 

 jection of the first, yellowish ; the third subtriangular, small, brownish, 

 and yellowish on the inner side ouly ; arista very slender, glabrous, half 

 as long as (he body, with a spatulate expansion at the tip, about one-third 

 of which at the base is white, the rest black (the antenna is like that of 

 T. moecJius, figured in Monogr., ii, tab. iii, f. 6, d, only the spatule at the 

 end has none of the emargination represented on the figure, and is like 

 tab. iv, f. 12, c). Face very long and narrow, somewhat broader below, 

 golden-yellow, but without luster. Cilia of the posterior orbit black ; tho- 

 rax metallic-green, with two distinct bluish lines on the dorsum, which is 

 very slightly grayish-pruinose, especially about the shoulders. Pleurae 

 somewhat yellowish-pruinose above the coxse ; abdomen metallic-green, 

 whitish-pruinose. Cilia of the tegul£e black ; hypopygium greenish, witli 

 a large patch of brownish-yellow velvety down near the root ; lamellae of 

 moderate size, reddish-yellow, with black hairs on the apical and yel- 

 lowish ones on the lateral edge. Prevailing color of the legs yellow ; 

 front coxae of the same color, dusted with golden-yellow 5 their extreme 

 root black ; front femora with scattered black pile on the outer side ; 

 front tibiae with a row of stiff", erect bristles on the inner side, and with 

 another row (^f still longer bristles on the outside ; both, when well pre- 

 served, extend beyond the middle of the tibia; front tarsi about the 

 same length with the tibiae, brownish from the end of the first joint; 

 these tibiae and tarsi, in a certain light, are silvery-pruiuose ; middle 

 femora blackish at the extreme root ; middle tarsi brownish from the tip 

 of the first joint; proximal half of the hind femora greenish-black; 

 knees infuscated ; hind tibiae black at tip ; hind tarsi black ; wings 

 subhyaline, rather short. Length 5-6™^". 



Hah. — Webber Lake, Sierra County, Sierra IsTevada, July 22. Two 

 males. 



T. sanus is very like T. moechus, which I used to find abundantly at the 

 Trenton Falls, New York; but the hind femora are broadly black at base, 

 the hind tarsi altogether black, which color also invades the tip of the 

 tibiae; the anteunal arista is much longer, the spatule at its end not 

 emarginate; the thorax has two blue longitudinal lines, etc. 



I have a female Tachytrechus from Sonoma County (July 6), which 

 evidently belongs to a third species. It has yellow legs; tarsi black; 

 tips of femora to a considerable extent likewise black; cilia of the pos- 

 .terior and inferior orbit whitish; thoracic dorsum yellowish-pollinose, 

 with a median brownish-coppery stripe, which is not pollinose, and stops 

 before reaching the scutellum; dorsal thoracic bristles inserted on brown 

 dots, etc. 



