188 THE ENTOMOLOGIST. 



suggests that Smith's supposed male of ajjinis does not belong to 

 it. The fact is, the original descriptions of both modesta and 

 affinis are such that it is little better than guesswork to identif} T 

 the species described. Mr. Eobertson, feeling this, goes so far 

 as to propose the alternative name zizice for the supposed affinis, 

 and until we can have a better description of the latter, from 

 Smith's type, it will be preferable, I think, to call the insect 

 ziz'ue, Bob. P. modesta may remain as identified by Eobertson ; 

 I have found it larger than zizice, though Eobertson gives the 

 same dimensions. 



Geographical Distribution. 



When studying the genus Perdita, I was fortunate in 

 having exact data concerning the localities and habits of most 

 of the species. With Prosapis, which is distributed all over 

 the continent, and presents few species in New Mexico, the 

 case has been entirely different. Consequently the difficulty 

 of correctly associating the sexes, and in many cases of deter- 

 mining the status of slightly-differing forms, has been very 

 great, so that the attempt was almost abandoned. The most 

 useful method for clearing up the difficulties alluded to is pro- 

 bably to consider separately the species seen from each State 

 or territory. 



Illinois. — Thanks to Mr. Eobertson, we are well acquainted 

 with the species of this State, which are not numerous, viz. 

 zizice, Eob., modesta, Say, pygmcea, Cress., saniculce, Eob., illino- 

 ensis, Eob., and nelumbonis, Eob. The first three seem to be 

 much commoner than the others. Dr. W. A. Nason sent me a 

 large series of specimens which he had collected at Algon- 

 quin, 111. ; they include zizice, modesta, pygmcea, and a single 

 nelumbonis. 



Iowa. — One specimen of P. saniculce has been seen. (Coll. 

 Amer. Ent. Soc.) 



South Dakota. — P. zizice, race dunningi, nov. One male, 

 Volga, S. D., sent by Mr. S. N. Dunning. Length, 5k mm. 

 Differs from zizice by the dullish and quite strongly punctured 

 first segment of abdomen, the somewhat more dusky wings, the 

 supra-clypeal mark long, nearly as in illinoensis, not notched at 

 tip, the lateral face-marks broadened and squarely truncate at 

 ends (not rounded or obliquely truncate), the face a trifle broader. 

 The mandibles are strongly bifid at tips, as in zizice. From 

 illinoensis it differs at once by the punctured first abdominal 

 segment, the yellow stripe on scape, and the partly black hind 

 tibia. From rugosula it differs by the more slender and curved 

 scape, with a yellow stripe, the lateral face-marks broader at 

 their ends, the flagellum distinctly pallid beneath, the yellow on 

 hind border of prothorax, and the smaller abdominal punctures. 



