28 DIPTERA OP NORTH AMERICA. [PART IV. 



facets of the upper and of the lower part of the eyes, nor a dis- 

 tinct dividing line between them. 1 The eyes are glabrous, except 

 in the Amalopina and in the genus Trichocera, where they are 

 pubescent. Ocelli are wanting, except in Trichocera, where 

 they are distinctly perceptible ; Pedicia also shows some traces 

 of them. 



The antennae are composed of a cylindrical, elongated first 

 joint ; a short, cyathiform or rounded second joint, and from 12 to 

 14 joints of the flagellum. The Anisomerina have an abnormal 

 number of joints (from 6 to 10) ; and in some foreign genera, the 

 number of the joints is larger (compare Gynoplistia, Cerozodia, 

 Ctedonia, etc.). The usual measure of the antennae is, that when 

 bent backwards, they nearly reach the root of the wings ; they 

 are much shorter than this in the genus Amalopis. The male 

 sex in the Anisomerina, especially in some American species of 

 Eriocera, has enormously prolonged filiform antennse, sometimes 

 three or four times the length of the body. Some Limnophilae, 

 also Gylindrotoma, have the antennae of the male considerably 

 longer than those of the female and pubescent on their whole 

 length; usually, however, this difference in length between the 

 sexes is much less perceptible. The male has often, on the under 

 side of the three or four basal joints of the flagellum, a dense, 

 short pubescence, which is much less perceptible in the female; 

 in some cases this pubescence extends on both sides of the whole 

 antenna. It is worthy of notice that when the antennae of the 

 male are long and pubescent, the first basal joint is very apt to 

 be shorter than usual ; this is the case for instance with Limno- 

 phila tenuipes, Cylindrotoma americana, Via, etc. Pectinate 

 antennae occur only in Rhipidia among the native species, but 

 several foreign Limnophilina have them also. 



The feet are long and slender, more or less pubescent ; the 

 presence or absence of spurs at the tip of the tibiae, of empodia, 

 and of teeth on the under side of the ungues constitute the basis 

 of the principal subdivisions of the T. brevipalpi, and will be 

 sufficiently noticed below. The spurs, whenever present, are two 



1 In the genus Blepharocera (fam. Blepharoceridce, Monogr. Vol. I, p. 8) 

 the eyes are divided in two portions, the upper one with large, the lower 

 one with small facets ; the upper portion is comparatively smaller in the 

 male than in the female ; in life, these portions differ in their color ; the 

 upper one, in B. capitata Lw., is reddish-green, the lower one purple. 



