218 ERNEST A. BACK. 



OIZONIAS. 



Dizoyiias Loew, Cent., VII, 53, 1866 



Dizonias Schiner, Verh. Zool.-Bot. Ges., 1866, 846; quotes orig. 



description. 

 Dizonias Williston, Biologia, Diptera, I, 305, 1901. 



Head obviously broader than high, quite thick; face and 

 front moderately broad; the face scarcely narrowed above, 

 the protuberance moderately convex and reaching nearly to 

 the base of the antennae and clothed throughout with stiff 

 hairs. Front but little depressed, ocellar tubercle not prom- 

 inent, but with bristles. Basal segments of antennae short, 

 cylindrical, the first about twice the length of the second, 

 the second short, swollen distally; the third elongate, over 

 twice the length of the first and second, without a style, on the 

 inner distal half with a distinct excision. Thorax moderately 

 convex above, with stout bristles upon the posterior callosities, 

 in an irregular row extending from before the base of the wing 

 backward and upward to above the callosities and upon the 

 scutellum. Abdomen cylindrical, not attenuated toward the 

 tip in the male, but slightly narrowed in the middle; in the 

 female slightly tapering toward the tip. Male genitalia small, 

 stout, not meeting to close the anal opening, thus giving the 

 tip of the abdomen a broken appearance as in Ceraturgus and 

 SphcBgeus; the female ovipositor with a circlet of spines; 

 empodia well developed. Wings quite broad; first posterior 

 cell wide open, the third very broadly open, the fourth closed 

 before the margin, the anal cell closed on the margin. 



Type. — Dizonias phcBnicurus Loew. 



The males of Dizonias, thus far known, are conspicuous in 

 that all have black wings, two whitish pruinose abdominal 

 fasciae, the posterior one emarginate, located near the bases 

 of the second and third segments; thus they are recognized 

 by their coloration as easily as by their structure. The female 

 differs very much from the male, being usually yellowish-red 

 with golden, instead of white, bands upon the abdomen; in 

 pilatei there are pruinose bands on segments 1-5. Dr. Wil- 

 liston in the Biologia says, "the dissimilar coloration of the 

 two sexes of the species of the genus and the uniformity of 



