PAKACOSMUS. — PHTHIEIA. 155 



PARACOSMUS. 



Paracosmus, O. Sacken, Western Diptera, p. 262 (1877). 

 Allocotus, Loew, Centur. x. no. 48 (nomen. praeoc). 



l. Paracosmus morrisoni, sp. n., $ . 



Black; hind margins of the abdominal segments white; legs rufous; wings hyaline. 

 Length 6-7 millim. 



Hab. Mexico, Northern Sonora (Morrison). 



Head black; a silvery mark, visible in a certain light only, on each side of the 

 mouth ; a small silvery triangle a short distance above the antennae, on each side, near 

 the orbit (a hoary dust seems to exist all along the orbit, but it is indistinct in my 

 specimen) ; occiput with a thin greyish-silvery pollen ; antennae black. Thoracic 

 dorsum with a white stripe on each side, the stripe reaching the scutellum and formed 

 by white pollen with some white pile upon it ; two narrower stripes, of an impure 

 white, in the middle, the distance between them being a little greater than the 

 distance from the lateral stripes ; in the intervals between these four stripes the 

 black ground-colour is somewhat modified by a microscopic, pollen-like, appressed, 

 yellowish pubescence ; pleura shining black, with a silvery stripe across its lower 

 portion ; scutellum black, shining, y ellowish-pollinose at the base. Knob of the halteres 

 yellowish-white. Abdomen black, but little shining ; segments 1-5 with a well-defined, 

 narrow, white posterior margin, becoming gradually narrower on each following 

 segment, especially on segments 4 and 5. Coxae black, the femora and tibiae rufous; 

 tarsi, except the base, black ; front and middle tibiae with a slight, microscopic, silvery 

 down. Wings hyaline. 



A single female specimen. 



N.B. — This is the second species of this remarkable genus; I dedicate it to its 

 lamented discoverer. 



PHTHIRIA. 



Phthiria, Meigen, in Illiger's Magazin, 1803; Klassif. 1804 (nee Wiedem., Rondani). 



l. Phthiria consors, sp. n., $ . 



(?) Phthiria cingulata, Loew, Linn. Entomol. i. p. 383. 



Black, with yellow marks ; four anterior femora more or less yellow at the base, the hind pair black ; wings 



tinged with pale brownish. 

 Length 4-5 millim. 



Hab. Mexico, Ciudad in Durango 8100 feet (Forrer). 



Head yellow, with a black line in the middle of the front, expanded into a trans- 

 verse spot above the antennae, and ending in the black ocellar spot ; occiput, except the 

 broad yellow orbits, black ; proboscis, palpi, and antennae black ; the third joint of the 



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