Descriptions of British Diptera. 211 



Finally, the wings assume an appearance very similar to those of the 

 Empides."* 



As is the case with the Bombylii, we are still unacquainted with 

 the previous states and metamorphoses of these insects. 



Phthiria pulicaria. 



Meigen, ii. 219; Macquart; Curtis, Brit. Ent. pi. 521 — Bomb, pulicarius, Mi- 



kan, Monog. pi. iv. fig. 14 — Volucella campestris, Fallen — Phthiria nigra, 



Meig. Klass, pi. x. fig. II. — Phthiria pygmaea, Latr. Gen. Crust, iv. 3.4. 



Male : deep black ; the hypostome clothed with white hairs ; 



forehead black : the abdomen more or less invested with whitish 



hairs; halteres dark-brown : wings nearly hyaline, the stigma brown ; 



legs black. 



Female : not so deep black as the other sex ; the hypostome white, 

 and the forehead, which is wide and of a dark-brown-colour, has two 

 white spots anteriorly ; thorax with a white stripe on each side, the 

 sides of the breast greyish, with two white spots ; scutellum black, 

 marked with a pale yellow point at the hinder extremity ; halteres 

 white ; wings purely hyaline. 1^ line. 



This appears to be everywhere a rare insect, and was not known 

 to inhabit this country till lately, when it was found by Mr Curtis 

 at Covehithe, in Suffolk. 



Genus PLOAS. 



Antennae about the length of the head, placed close together 

 at the base, diverging above ; first joint thick, conical, 'and hairy ; 

 second cup-shaped, hairy ; third rather long, slender, naked 

 and fusiform, slightly compressed, and terminating in a short two- 

 jointed style : proboscis not much longer than the head : pal- 

 pi cylindrical, terminating in a small sharp point: labrum nearly as 

 long as the proboscis, obtuse ; tongue as long as the proboscis, and 

 pointed : eyes contiguous in the male, remote in the female ; the 

 crown with three ocelli ; thorax oval, the surface elevated : wings 

 with three submarginal cells, the first posterior one open ; legs slen- 

 der. 



The most distinctive character in this genus, which was esta- 

 blished by Latreille, is the thickness of the radical joint of the an- 

 tennae. The proboscis also is much shorter than in the other mem- 

 bers of the same family, so that the insects are obliged to settle on 

 the corolla of flowers to obtain food, instead of sipping it while on 



* Diptcres du Nord de hi France. 



