Sept.,i9oi.] Webster: Southern Corn-Leaf Beetle. 131 



about the roots of these same species of Aster found great numbers of 

 a coleopterous larvre which from their resemblance to the larvae of other 

 Eumolpini seemed likely to be those of Myochroits denticollis, but 

 again, on account of the attack of Sporotrichiim, only a single adult 

 has been reared and that a Paria. 



By the accompanying map, Plate IX, I have endeavored to illustrate 

 the known distribution of this and the other two species of the genus 

 Myochrous, not as in any way throwing additional light upon the food 

 habits of M. denticollis, though one of them, M. sqtiamosus, seems to 

 have the habit of collecting under dried excrement of the Bison, when 

 these existed in its area of distribution, and, later, under the dried ex- 

 crement of cattle. Mr. Dury tells me that he always collected M. denti- 

 collis under boards and similar objects laying on the ground, and on 

 low lands. 



In their distribution, M. denticollis inhabits the country east of a 

 line drawn from southwestern Iowa to Tucson, Arizona, while M, 

 sqiiamosus ranges from northern Arizona and New Mexico to the 

 Platte River in Nebraska and northwest into Montana, probably 

 through western South Dakota and Wyoming. M. longiilus, the only 

 remaining species of the genus to be mentioned, is known to range 

 from southern California and Arizona, northward into Colorado, where 

 it has been reported by LeConte, without exact locality. It not un- 

 likely occurs also in Utah, though it has not yet been reported from 

 there in our literature, so far as I am able to learn, but in any case 

 overlapping the territory inhabited by M. sqitamosus in northern Ari- 

 zona and New Mexico, and also, probably, in Colorado, while the 

 latter species borders on and possibly mingles with M. denticollis in 

 southwestern Arizona, eastern New Mexico, western Kansas, and, 

 probably, extreme southeastern Nebraska. 



In their anatomical affinities, denticollis is the most remote from 

 sqiiamosus, though their habitat is contiguous if not indeed overlapping, 

 and the nearest to longulus, whose habitat is far to the south, and only 

 touching in Arizona. Thus is would seem that the first two had been 

 the earliest species to push northward, and have become the most 

 widely separated in structure, while longulus seems to have been the 

 latest to enter our fauna. The genus Diabrotica offers some very good 

 illustrations of the evolution of species along the west coast, inde- 

 pendently, as it would appear, from those along the eastern shores. 

 Hence,.']/! longulus might very probably represent a west coast variation. 



