64 ‘ THE ACRIDIIDAE OF MINNESOTA 
cal, projecting from the prosternum between the front legs. The face 
is vertical or nearly so in all save the first genus. The head is rela- 
tively smaller and less swollen than in either the Tryxalinae or the 
Oedipodinae. The disk of the vertex is not sunken or concave, its lat- 
eral carinae are low and rounded or often obsolete; foveolae are com- 
monly wanting or indistinct. The disk of the pronotum is normally 
flat or nearly so and is never strongly tuberculate or rugose; its pos- 
terior margin is never acute-angled but usually rounded or subangulate. 
The antennae are relatively short and composed of from twelve to 
twenty-five joints. Tegmina may or may not be present and, when 
present, vary from the length of the pronotum or less to forms longer 
than the abdomen. The inner wings, when present, are transparent, 
usually vitreous, and never brightly colored. The posterior femora are 
well developed and the members of this group are in general strongly 
saltatorial. 
This subfamily includes most of the species which are of economic 
importance within our area and indeed throughout the world, the truly 
destructive locusts, save for certain Tryxalinae. It includes nearly all 
of the truly migratory species together with a very large number of 
species which, while non-migratory, are at times extremely destructive 
to growing crops. The enormous damage resulting from the invasions 
of the Rocky Mountain locust, Melanoplus spretus, causing losses at 
one time placed at over $200,000,000 in the Middle West, is an ex- 
ample of the economic importance of one of the migratory species, 
while the annual loss from our non-migratory species, although it can 
not be accurately estimated, since, being yearly, our crop returns are 
adjusted to it, would be equally startling if it could be expressed in 
dollars. It is safe to say that if we could but eliminate these estab- 
lished and unnoticed pests for one year, the crop returns would be 
enormously increased. In this group the “music” or stridulation of 
the males appears to be confined to the one method of rubbing the 
hind femora against the edge of the tegmina. This is, of course, weak 
“music” as compared with the loud calls of some of the Locustidae, 
but even in the case of certain brachypterous forms, the males have 
been seen to go through the.motions although no sound was audible 
to the listener. Some of the species of Schistocerca produce a faint 
rustling sound with the wings when in flight but there is nothing ap- 
proaching the definite and controlled aerial stridulation of some of the 
members of the Oedipodinae. In general the coloration of the mem- 
bers of the subfamily is of varying shades of dull brown, although a 
few are rather strongly colored. Classification of this group is based 
in large part upon the ventral sclerites and the genitalia of the males. 
The following key will serve to separate the genera of this subfamily 
which are represented in Minnesota : 
