AKT. 37. FLIES OF THE GENUS TACHYTRECHUS — GEEENE. 15 



No. 24784. U.S.N.M.) and four specimens deposited in United States 

 National Museum by J. M. Aldrich. 



12. TACHYTRECHUS MOECHUS Lotw. 



Fig. 12. 



Tachytrechus moechus Loew, Neue Beitraege, 1861, vol. 8, p. 40, .spec. 1. 

 MaceUocerus moechus Loew, Mik, Dipterologische Untersuchungen, 1878, 

 p. 5, No. 3. 

 Male. — Face long and narrow, about twice as wide on the lower part 

 as it is just below the antennae, reaching the lower edge of the eyes, 

 covered with a golden yellow dust, dull, front deep green, nearly 

 dull, in certain lights covered with a brown dust. Antennae mostly 

 deep yellow, first joint thick, about four times longer than the second 

 and third joints together, second joint very rudimentary, third joint 

 somewhat rounded and dark brown on apical half to three-fourths; 

 arista a little longer than the head, black, slightly thickened at base, 

 lamella large, black, nearly as wide as long, slightly emarginate on 

 apical edge, with a very small, white area where it joins the stem. 

 Orbital cilia black on apical third, white below. Thorax and scutel- 

 lum shiny, deep bronze-green in certain lights dull, covered with a 

 bronze dust. Abdomen metallic bronze green, in certain lights with 

 a silvery dust more prominent on basal portion of segments, a narrow 

 blackish area along the apex of each segment. Hypopygium large, 

 blackish green, the green more noticeable at the apex, lightly covered 

 with a yellow dust which is denser near the middle, lower edge on 

 the sides shiny, reddish-black; lamellae deep yellow, rounded, hair 

 black, short, longer on edges. Legs deep yellow, tips of middle and 

 hind tibiae and front tarsi in certain lights slightly infuscated ; middle 

 and hind tarsi deep brown. Sometimes a trace of yellow on the 

 basal half of the middle and hind tarsi. Front coxae yellow, blackish 

 along basal edge ; middle and hind coxae blackish gray and yellowish 

 at apex. Wings faintly ^^ellowish-brown ; halteres yellow, slightly 

 darker at base of stem; tegulae pale yellow with long black cilia. 



Female. — Like the male except the differences noted. Face just 

 below the antennae about three-fourths as wide as at the lower part. 

 Antennae with first joint smaller, more reddish-yellow, less swollen; 

 second joint same color as first, less abortive than in the male; third 

 joint rounded, brownish-black, reddish-yellow only on the inferior 

 side of basis. Arista bare, black, tapering gradually to the tip. 

 Abdomen with a little more green. All coxae grayish-black coated 

 with a silvery dust, apex dull, pale yellow; femora brownish-black 

 with a silvery dust, extreme base of femora, apical fourth of the front 

 femora, front tibiae entirely, and basal half to two-thirds of the hind 

 and middle tibiae reddish-yellow ; apical portion of middle and hind 

 tibiae and all tarsi brownish-black. 



