206 BiLLiynx 31, inited states national museum. 



Triodonta curvipes. (Plate IX, figs. 1, lo, Ih, Ic, Id.) 



Mirodon ciirvipts Wiedemanu, Auss. Zw. Ins., ii, 149, 3. 

 Helophilntt alhicepn Macquart, Dipt. Exot. ler Suppl., 132, 9 ; pi. fig. 7. 

 Pohjdonta hicolor Macquart, Dipt. Exot. 4e Suppl., 144, 1 ; pi. xiii, fig 6. 

 Pohjdonta curvipes Ostt'u Sacken, West. Dipt., 338; Williston, Proc. Am. Phil. 

 Soc, XX, 3-24. 



Habitat. — New England!, Colorado, California (O. S.). 



^ , 9 . Length, 10 to l.'i'""^ Face black, shining on the tnbercie and the 

 cheeks ; elsewhere thickly covered with yellowish pollen and pile. An 

 tenna^ black ; arista yellowish at the base and end. Front in male black 

 on the ui)per part and above the base of the antennae; elsewhere covered 

 with yellowish dust. In the female the front is broad, shining in the 

 middle below, blackish above, pile near the ocelli blackish ; on the oc- 

 ciput white. Thorax black, covered thickly with a brownish dust, leav- 

 ing faint indications of a slender median and lateral stripes, and with 

 short, rather abundant, obscure, yellow pile. Pleurre dnsted with white; 

 scutellum sub-translucent yellow. Abdomen with short pile; in the 

 male as follows: First segment black ; second segment black in front, 

 except at the sides, dilated iu the middle in a broad sub-triangular si)ot, 

 reaching two thirds of the length of the segment ; remainder of the 

 abdomen yellowish red; in the femaleblack, partly shining; first segment 

 and second, except posterior i)art, thickly dusted with grayish ; third 

 and fourth segments on the front part with a broad interrupted band 

 of the same dust ; on the fourth sometimes only two rounded spots. 

 Legs black ; tip of femora and base of tibiae yellowish red. Wings 

 nearly hyaline. 



Numerous specimens. 



TROPIDIA. * 



Tropidia Meigen, Syst. Beschr., iii, 346, 1822. 



Medium sized, nearly bare species ; black, with yellow markings on 

 the abdomen. Head hemispherical, somewhat broader than the thorax. 

 Antennae short, third joint rather large, not much longer than broad, 

 the anterior angles only a little rounded ; arista bare. Face with a 

 median keel-like ridge; not produced, obliquely truncate; cheeks narrow 

 below the eyes. Eyes bare, contiguous in the male. Thorax short and 

 rather broad. Scutellum large, its border thin; more or less yellow. 

 Abdomen narrow, somewhat elongate, of nearly equal width, depressed. 

 Wings folded together in rest; marginal cell open, third vein with a 

 moderate curvature, sometimes deeply bent into the first posterior cell, 

 anterior cross-vein beyond the middle of discal cell, oblique. Legs 

 strong; hind femora extraordinarily thickened, below near the outer 

 end with an angular projection ; hind tibiae bent. 



* Tpontdia, a keel. 



