280 DIPTERA OF NORTH AMERICA. [PART II. 



tarsi and the proportionally somewhat lesser length of the first 

 joint of the hind tarsi seem to prove its distinctness sufficiently. 



b. Tarsi but little infuscated towards the end. 



«. All the eoxse entirely yellow. 



IS. P. Tricolor Loew. 9 • — Viridis, nitidissimus, proboscide, palpis, 

 duobus primis antennarum articulis, abdominis basi et maculis laterali- 

 bus, ventre, coxis pedibusque flavis. 



Green, very shining ; proboscis, palpi, the two first joints of the antennae, 

 the basis of the abdomen and spots on its side, venter, coxae and feet 

 yellow. Long. corp. 0.13—0.14. Long. al. 0.13—0.14. , 



Syn. Psilopus bicolor Loew, Neue Beitr. VIII, 96, 15. 



Green, very shining. Palpi and proboscis yellow. The gla- 

 brous face and the front bluish-green, the former rather closely 

 dusted with white, the latter with the usual black bristles, which 

 have but an insignificant length, otherwise without pubescence. 

 The two first joints of the antennae yellowish ; the second with 

 only extremely short minute black hairs. The black bristles of 

 the thorax short. Scutellum with only two long black bristles. 

 Pleurae closely dusted with white, their hind margin yellow. First 

 segment of the abdomen yellow, with a shining green hind mar- 

 gin ; the second segment likewise yellow, with a very large metallic- 

 green spot, which only leaves unoccupied the basal one-third, the 

 anterior corner and the lateral margin ; the two following seg- 

 ments shining green, with a yellow anterior corner and yellow 

 lateral margin ; the fifth segment only with a yellow lateral mar- 

 gin. Yenter entirely yellow. The pubescence of the abdomen 

 is scarce, delicate and short, upon its upper side black ; the minute 

 black bristles before the incisures are so short that they distinguish 

 themselves but little from the remaining pubescence. All the coxae 

 and the very glabrous, long and slender feet pale yellowish. Fore 

 coxae with a short whitish pubescence and with a few hair-like 

 'whitish bristles. Under side of the fore femora with extremely 

 short minute whitish hairs, under side of the middle and hind 

 femora glabrous. Fore tibiae entirely without bristles ; middle 

 and hind tibiae with one short minute black bristle upon the out- 

 side, not far from the basis and with some similar minute bristles 

 at the tip. The very slender fore tarsi over once and two-thirds 

 the length of the tibiae ; their first joint a little longer than the 



