REMARKS ON THE GENERIC CHARACTERS. 



the eyes are excised near the antennae ; the feet have rough bristles, and 

 the first joint of all the tarsi is much longer than the second. 



Among all genera of the Second Sub-division Psilopus is distin- 

 guished by the slender structure of its body, and especially of its feet, its 

 very broad and more or less excavated front, the smallness of its antennae, 

 and finally by its fourth longitudinal vein, which is provided with a pos- 

 terior branch. I have assigned to it a position altogether at the end of 

 the second sub-division, and will revert to it there. The other genera of 

 this sub-division may be distributed into two groups according to the struc- 

 ture of the thorax. To the first group belong those genera, the upper side 

 of the thorax of which is convex, as far as the scutellum (No. 24-39) ; to 

 the second those, where the upper side of the thorax, before the scutellum, 

 bears an inclined, more or less concave, area (No. 40-43). 



The genera belonging to the first group, and possessing a sixth longi- 

 tudinal vein, form the first sub-group ; those where this vein is wanting, 

 form the second sub-group. ' 



The first sub-group contains either such genera as have the transverse 

 vein not close to the posterior margin of the wing, or such where an 

 approximation of that kind takes place in a striking manner. The genera, 

 where there is no striking approximation of the posterior transverse vein 

 to the margin of the wing, are : Thinophilus (24), Peodes (25), Nemato- 

 proctus (26), Leucostola (27), Eutarsus (28), Diaphorus (29), Lyroneurus 

 (30),Chrysotus (31), Teuchophorus (32), Sympycnus (34), Campsicnemus 

 (33), and Plagioneurus (36). Thinophilus has the small and but little 

 imbedded hypopygium in common with Peodes (in all the other genera 

 that belong here, it is much more imbedded) ; it differs from Peodes by the 

 structure of the face, which, in both sexes, is broader below, and has an 

 angular margin ; by the large palpi of both sexes, and the very small size 

 of the interior appendages of the hypopygium ; the first two joints of the 

 antennae are small, the third somewhat in the shape of a lens, and the 

 arista dorsal ; the last segment of the fourth longitudinal vein, towards its 

 end, is parallel, or almost so, to the third longitudinal vein ; the feet of the 

 male are usually variously adorned. The structure of the body of Peodes 

 resembles in general that of Thinophilus ; the structure of the antenna; 

 and of the wings is also nearly the same, only the parallelism of the third 

 and fourth longitudinal veins is still more complete than in most of the 

 species of Thinophilus ; both of the interior appendages of the hypopygium 

 form a large horny forceps ; the tarsi of the male of the only species 

 hitherto known are plain. 1 The species of Nematoproctus, in the 

 whole structure of the body, are nearest the species of Porphyrops ; they 

 can be, however, easily distinguished from them by the rounded, and in 

 both sexes small, third joint of the antennas, and by the arista, which is 

 inserted in the neighborhood of the basis. They are less closely related 

 to the genus Leucostola, because the elongation of the first longitudinal 

 vein, the broad shape of the wings, and the subapical position of the arista 

 are wanting in them ; the same characters and the glabrousness of the 



