16 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.6©. 



Length 4.5-5 mm. 



Type locality. — Trenton Falls, New York (Osten Sacken), 



Type. — In Museum of Comparative Zoology, Cambridge, Massa- 

 chusetts. 



Distribution. — Lafayette, Indiana, June 8 to July 6, 1915, J. M. 

 Aldrich ; Algonquin, Illinois, no date ; a specimen marked " N. H." 

 with no date; four specimens deposited in United States National 

 Museum Collection by J. M. Aldrich; Franconia, New Hampshire, 

 Mrs. A. T. Slosson, collection United States National Museum. 



13. TACHYTRECHUS SANUS OBten Sacken. 



Fig. 11. 



Tachytrechus sanus Osten Sacken, Western Diptera, 1877, p. 316. 

 Macellocerus sanus Osten- Sacken, Mik. Dipterologische Untersuchungen, 

 1878, p. 5, No. 3. 



Male. — Face about as long as eye height, just below antennae 

 about one-third as wide as at lower end, golden yellow, without 

 luster; front rather dull, dark green, slightly darker in center and 

 on the ocellar triangle, ocelli yellowish. Antennae yellow, first joint 

 large, reddish-yellow, beset with black hairs above longer near the 

 tip ; second joint quite small, placed on the other side of a projection 

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

 on the inner side only ; arista slender, nearly twice as long as height 

 of head, lamella black, fairly large and snow-white at base, straight 

 on upper edge. Orbital cilia black. Thorax metallic-green, with two 

 distinct bluish lines on the dorsum, which is very slightlj'^ grayish- 

 pruinose, especially about the shoulders. Scutellum metallic-green. 

 Abdomen metallic green, in certain lights whitish pruinose with the 

 apical edge of each segment brownish-black. Hypopygium greenish, 

 with a large patch of brownish-yellow velvety down near the root, 

 long hairs yellowish, those on the side black, in certain lights there is a 

 purplish hue on the apical half; lamellae of moderate size, with yel- 

 lowish cilia on the sides and black on the apical edge. Prevailing 

 color of legs yellow ; front coxae of same color dusted with golden yel- 

 low, their extreme root blackish; front, middle, and hind femora, ex- 

 cept the base of the latter, all tibiae except the tip of the hind pair and 

 front tarsi except last joint yellow, basal two thirds of middle meta- 

 tarsi yellowish ; front tibiae and tarsi with a silvery dust ; middle and 

 hind tarsi, extreme tip of hind tibiae, base of hind femora and last 

 joint of front tarsi brownish-black; front tibiae a row of large black 

 macrochaetae on the front and outside, those of the latter are broader, 

 between these two rows is a row of short bristly hairs. Middle tibia 

 has one large, black macrochaeta on the inner flexor side, near the 

 apex. Wing hyaline ; halteres deep yellow slightly infuscated at the 

 base of the stem ; tegulae pale yellow, cilia long, black. 



