REHN AND HEBARD 57 



similar body bulk to the single female of robustum, while their 

 spineless character shows they in all probability belong to a 

 smaller individual of a different species of the genus. The color 

 of the cephalic and median tibiae and all of the other color fea- 

 tures of robust um are those of nigripes, while the peculiar features 

 of the lateral lobes of the pronotum of this species are well 

 described. 



This species is closely related to 0. laticauda, which it replaces 

 throughout the central valley and prairie region of the United 

 States. The eastern species, laticauda, has on numerous occa- 

 sions been mistaken for nigripes and so recorded, but there need 

 be no confusion of the two forms after they have once been 

 compared. The shape of the lateral lobes of the pronotum alone 

 serves as a ready means for separating the species. We have seen 

 two specimens of this species from Lafayette, Indiana, which 

 show practically no black on the tibiae. 



In size this species shows much the same features as laticauda, 

 averaging smaller in the northern portion of its range and larger 

 in the southern, but individual variation is everywhere evident. 

 The caudate winged type is typically represented by two females, 

 one from Lincoln, Nebraska, and the other from Victoria, Texas. 

 In addition a number of both sexes have the tegmina and wings 

 more elongate than in the majority of the series. Two specimens 

 in the present series have the caudal femora spined on the ventro- 

 internal margin. 



Distribution. — The central valleys and prairies of the United 

 States, from as far north as the shores of the Mississippi in 

 Minnesota (Lugger), south to New Orleans (Redtenbacher) and 

 Victoria, Texas, east to Point Pelee, southern Ontario (E. ^L 

 Walker), Columbus, Ohio, and Clarksville, Tennessee, west as 

 far as Gering, on the Platte River, in western Nebraska and 

 Denver and "Rocky Mountains" (Redtenbacher), Colorado. 



Specimens Examined: 68; 23 cf, 43 9,2 juv. 9 . 

 Columbus, Ohio (C. M. Mead), 1 9, [Hel)ard Cln.]. 

 Indiana, (W. S. Blatchjey), 3 d", 4 9, [Hebard Cln. and Morse Cln.]. 

 Lafayette, Indiana, X, 14, 1913, (H. Fox), 18, 1 9, [A. N. S. P.]. 

 Vigo County, Indiana, (\V. S. Blatehley), 1 cr\ 1 9, [Morse Cln. and U. S. 

 X. M.). 



Goose Pond, Indiana, IX, tj, 1892, (Blatchley), 1 9, [f. S. X. M.]. 

 Illinois, 1 o^,[M.C. Z.|. 



THA.NS. .\.M. HN'T. SOC, XLl. 



