308 ERNEST A. BACK. 



[Note. — Since leaving Amherst I have been informed by Mr. Coquil- 

 lett that a specimen of Plesiomma, named by myself unicolor, is the 

 same as Schiner's longiventris . This being the case, longiventris be- 

 comes a synonym of unicolor, being published in Verh. Zool.-Bot. Ges., 

 1867, p. 375. The specimen in question agrees with Loew's type of 

 unicolor and comes from the type locality. 



HOLCOCEPHALA. 



|| Discocephala Macquart, Dipt. Exot., I, 2, 50, 1838. 

 Holcocephala Jaennicke, Neue Exot. Dipt., 51, 1867, name 

 changed. 



Rather small species. Head very much broader than the 

 thorax (PI. V, fig. 4) and strongly compressed anterio-poster- 

 iorly, hence the old generic name, Discocephala. Eyes pro- 

 portionately very large, giving the head a "goggle-like" 

 appearance; the facets on the fore part very large, but grad- 

 ually decreasing toward the upper, outer and lower margins. 

 Face broad, not at all swollen, somewhat excavated along 

 the orbits; mystax sparse and confined to the oral margin. 

 Antennae small, not closely approximated; first two segments 

 very short, rounded, with weak bristles above and below; 

 third segment cylindrical, twice the length of the first two 

 segments taken together; style well developed, distinct, prox- 

 imally nearly as broad as the third segment, distally narrowed 

 to a point. Front deeply excavated; ocellar tubercle large, 

 prominent. Proboscis weak; palpi small, cylindrical, almost 

 as long as the proboscis and terminated with long pile. Thorax, 

 strongly arched, without bristles; scutellum without pile or 

 bristles. Abdomen variable but never longer than the wings, 

 more or less, or not at all, coarctate. Male genitalia in part 

 composed of a pair of lateral lamellae above, a pair of long 

 slender forceps originating from the venter of the last segment 

 and curved upward, and a prominent, three-pronged penis, 

 curving downward and backward between the forceps. Hind 

 tibiae swollen distally, and the metatarsi much enlarged in 

 the male, not as much so in the female and at least twice as 

 long as the following segments ; legs sparsely clothed with fine 

 pile and bristles, the latter on the femora confined to the 

 lower side; the front tibias without a terminal claw-like spur. 



