72 



UNITED STATES NATIONAL MUSEUM BULLETIN 22 4 



separated posteriorly by a membrane; postmetacoxal 

 area clearly membranous, the tegula with 3 or 4 rather 

 long, slender bristles. 



Legs: The femora are moderately stout without be- 

 ing swollen; the hind femur without distal dilation. 

 Hind tibia relatively more thickened, the ventral sur- 

 face nearly plane, the dorsal surface rather strongly 

 arched. The dorsal pile of the anterior and middle 

 femora is short, appressed and setate; on the hind 

 femur the pile is longer and nearly erect or suberect, 

 its medial pile shorter and more nearly appressed. 

 True bristles are almost entirely absent on the legs 

 of these flies, except on the tarsal segments and be- 

 neath the posterior and middle femora, but on the 

 femora and tibiae there are some long, slender, bristly 

 hairs regularly arranged, the following complement 

 being present: several long bristly hairs on the outer 

 half of the dorsal surface of the hind femur; a row 

 of 5 very long, distinct, but slender bristles on the 

 basal half ventrally ; and on the hind tibia a dense, dor- 

 sal and ventral fringe of stiff, bristly pile, equally dense 

 but shorter laterally and medially. All tarsal segments 

 with long, dorsal terminal bristles. Ventromedial 

 aspect of the hind femur and the basal half or more 

 of the dorsal aspect with moderately long, dense fringes 

 of stiff pile. Middle femur with 3 or 4 long, bristly 

 hairs dorsally on the outer half and 7 or 8 slender, long 

 bristles, or bristly hairs ventrally. Middle tibia and 

 basitarsus moderately stout and with fringes of pile 

 on all four sides similar to those of the hind tibia, a 

 little longer dorsally and ventrally and with a row of 

 4 slender, anterior bristles which are distinctly longer 

 than the pile ; this tibia has 4 dorsal bristly hairs, 5 or 

 6 posteroclorsal and 4 ventral, bristly hairs. Anterior 



femur with some long, stiff pile ventrally and 5 or 6 

 slender, bristly hairs dorsally in addition to short ap- 

 pressed setae. Pile of anterior tibia much less con- 

 spicuous. All tarsi have well developed pul villi ; slen- 

 der, short empodia ; and sharp claws. 



Wings: The wings are broad, the marginal cell is 

 open, all posterior cells and the anal cell widely open 

 or closed in the margin. Only 4 posterior cells are 

 present. Posterior crossvein present. Alula as wide 

 as the costal cell ; ambient vein complete. 



Abdomen: The abdomen is broad, comparatively 

 short and depressed, widest at the end of the second 

 tergite, where it is as wide or slightly wider than the 

 thorax. It is a little narrowed beyond the second ter- 

 gite and without dorsal, membranous areas. There are 

 eight tergites in the male, the eighth from one-half to 

 three-fifths as long as the seventh, the third to sixth 

 tergites of equal length, the seventh only a little shorter 

 than the sixth and approximately as long as the first. 

 The second tergite is nearly as long as the third and 

 fourth combined. Female with eight tergites; the 

 eighth being two-thirds as long as the seventh. Pile of 

 the abdomen fine and short, except laterally, where it 

 becomes a little longer and more erect. Sides of the 

 first tergite with short, fine pile; sides of the second 

 tergite with abundant, long pile ; bristles absent. Male 

 terminalia short, inconspicuous, not rotate, more prom- 

 inent on the ventral portion where the lateral processes 

 are comparatively long and stout. Female terminalia 

 quite short; the ninth and tenth elements together no 

 longer than the eighth tergite. 



Distribution : Oriental. Trigonomima apipes Ender- 

 lein (1914) ; canifrons Enderlein (1914) ; cyanella 

 Osten Sacken (1882) ; pennipes Hermann (1914). 



Tribe Laphystini 



The flies of this tribe are never large; usually they 

 are medium size, and they present a robust appearance 

 for the most part, with short, appressed pile. A few 

 have fine, dense, erect pile or dense, curly, glittering, 

 appressed pile. The species of Psilocums Loew are 

 comparatively slender. These genera constitute the 

 group Prytanini of Hermann, a name which should be 

 discarded, because it is not based on any genus. 



The members of this tribe are readily recognized in 

 males because with few exceptions the number of visible 

 male segments is limited to 6, and the females have 

 tergites 6 and 8 greatly reduced to linear proportions. 

 Also, in many of the genera the marginal cell is closed 

 at the margin of the wing, which together with the 

 general form and frequent prominence of strong tergal 

 bristles seems to ally these with Laphriinae. 



Some workers with Asilidae express the view that the 

 Laphystini should be placed in the subfamily La- 

 phriinae. With this view I cannot concur. I regard 



them as an example of convergent evolution and point 

 further to the fact that of nearly 20 groups placed in the 

 tribe, the members tend to fall into 2 divisions with the 

 marginal cell either widely open or closed in the margin. 

 I believe, however, that the Laphystini are certainly 

 close 10 the stock which led to the Laphriinae, a conclu- 

 sion strengthened by the bulblike, ventral development 

 of the terminalia in Helolaphyctis Hermann and Ho- 

 plistomerus Macquart. It should be noted, however, 

 that when the marginal cell is closed the second vein is 

 generally if not always recurrent, a peculiarity unique 

 to the group and not present in Laphriinae. Their 

 generalized character is further shown by the simple 

 female terminalia; hence, I place them near the 

 Dioctrini. 



The adults frequent mud or wet sand banks and are 

 sometimes found in arid situations such as the baked 

 earth about desert rosette plants beneath which they hide 



