80 THE ACRIDIIDAE OF MINNESOTA 
with squarish dark spots. Hind femora variable in color; hind tibiae 
glaucous. The peculiarly expanded cerci, together with the minute 
furcula, should readily serve to distinguish this species, which has, as 
yet, been taken only from Ottertail County. 
Melanoplus atlanis Riley 
Melanoplus atlanis is extremely closely related to M. spretus Uhl, 
the formerly dreaded Rocky Mountain locust. It is one of the few 
species which ever become serious pests within our area. In size and 
general coloration (Plate II, 7), it 1s also very ‘similar’ toqous 
common or red-legged locust, M. femur-rubrum, from which species, 
however, it may be easily distinguished by the distinct apical notch in 
the subgenital of the male, while in M. femur-rubrum the subgenital is 
relatively broad with no notch at the apex. The differences which 
serve to separate this from M. spretus, however, are less distinct. The 
accompanying table will serve to show the close relationship of these 
three species. 
From this table it may be seen that while it is easy to sep- 
arate the males of M. femur-rubrum from the two related species by 
the differences in the cerci and subgenital plate, yet between MW. atlanis 
and M. spretus the only structural differences which may be noted are 
extremely small and, in fact, easily within the limits of variation of a 
single species. Indeed the real differences are even less than the table 
would indicate, when local variations are considered, as the table is 
based upon descriptions from Scudder’s Revision of the Melanopli 
(Proc. U. S. Natl. Museum, Vol. XX) and the measurements there 
given for M. atlanis are all admittedly of material in large part east- 
ern, while in M. spretus all are western. Another fact worthy of no- 
tice is that in certain specimens taken in Minnesota and Iowa the char- 
acters blend. For instance, in certain specimens which we have exam- 
ined, the measurements and the apical notch of the subgenital would 
indicate MV. atlanis, but the tegmina surpass the hind femora by the 
length of the head and pronotum combined. In fact the real basis for 
separation seems to lie mainly in the extended migrations of one form, 
while in the other the migrations although occurring are of but local 
extent. For some years it has seemed to the writer that these two 
insects, M. atlanis Riley, and M. spretus Uhl., may be considered pos- 
sibly as widely separated forms of a single variant species, the one 
being limited to the arid soils of the Rocky Mountains and their foot- 
hills, while the other is generally distributed throughout a large part 
of North America. Within this State M. atlanis, as already men- 
tioned, has proved a pest of really serious importance at various times. 
It hatches normally about the middle or latter part of May and with 
