8 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 82 



ity simply geographic races. The Atlantic coast specimens of gla- 

 hrata, arizonae^ procera^ fmnata, and latifroiis are obviously differ- 

 ent from the Arizona or Colorado ones, being either paler or darker 

 in color, usually larger, and, in glabrata and a7'i3onae, having deeper 

 punctation; but specimens from intermediate localities are interme- 

 diate, and throughout the series the structural characters and aedea- 

 gus remain the same, so that the difference must be considered only 

 varietal. 



In other species of the genus the change in characters correlated 

 with distribution has apparently gone a step further and becomes so 

 great that distinct species have arisen. Such is the case in Iwibi- 

 collis. This species, which is confined to the Pacific coast, is plainly 

 very closely related to uniguttata^ and probably derived from it, but 

 has developed certain distinctive characteristics that appear to be 

 specific. This may be the case, also, in latiovittata, which occurs 

 only in the Pacific and Northwestern States, and which is closely 

 related to alternata. 



In the discoidea group there seems to be an intermediate stage in 

 the development of species. In this group the differences in colora- 

 tion of specimens are very striking, but the shape, sculpture, ae- 

 deagus, and other structural characters are so similar that, aside 

 from the coloring, the forms are difficult to differentiate. Possibly 

 they are but varieties of a single species. D. leptolineata from Flor- 

 ida and texana from Texas, both closely related to discoidea^ are 

 doubtfully distinct. D. antennata^ an entirely pale beetle, would be 

 indistinguishable were it not for its entire lack of elytral vittae. 



Some of the species with blue or green elytra, such as xanthoTnelas, 

 triangularis^ and collata^ are widely distributed. In both xanthome- 

 las and collata there is considerable variation in color, size, and de- 

 gree of punctation, with the result that in each case two forms, 

 based primarily on color differences and not structurally separable, 

 have been described as species. 



LIFE HISTORY 



The life histories of four species of Dlsonycha have been published. 

 F. H. Chittenden has given an admirable account of the eggs, larvae, 

 and feeding habits of xanthomelas ^^ and a shorter account of the 

 life history of collata {meUicollis)'^'' and also glabrata}^ H. Gar- 

 man ^^ has also written a full account of the life history of glabrata. 

 W. E. Whitehead ^° has made a careful study of the life historj^ of 

 latifrons. 



"Chittenden, U.S. Bur. Ent. Bull. 19, p. 80. 1S99. 



" Chittenden, U.S. Bur. Ent. Bull. 82, p. 29, 1912. 



18 Chittenden, Bull. Brooklyn Ent. Soc, vol. 17, p. 147, 1922. 



1" Garman, 2d Ann. Rep. Kentucky Agr. Exp. Sta., p. 28, 1889. 



«> Whitehead, Nova Scotia Ent. Soc. Proc, 1918, p. 38. 



