Cockroaches, Locusts, Grasshoppers, and Crickets 147 
clear and transparent; the prothorax looked at from above appears to be 
“pinched” at its middle. The males make a loud crackling when in the 
air. 
It is familiar knowledge that locusts which are readily seen in the air 
are extremely difficult to distinguish when alighted. This concealment, 
resulting from a harmonizing of the body color with that of the grass or 
soil, is of course an advantage to the locust in its “struggle for existence” 
and is technically known as protective resemblance (see Chapter XVII). No 
locusts show this protective resemblance better 
than the species of Trimerotropis (Fig. 193) 
especially familiar in the western states. The 
colors of various individuals of a single species 
vary with the soil colors of the locality, ranging 
from whitish to 
brownish to slaty 
and bluish. I have 
taken series of spe¬ 
cimens of Trimero¬ 
tropis sp. in Colorado 
showing this whole 
range of ground 
coloration. 
Fig. 192. 
Fig. 193. 
Fig. 192. —Mestobregma cincta, male. (After Lugger; natural size indicated by line.) 
Fig. 193. —The maritime locust, Trimerotropis maritima, female. (After Lugger; nat¬ 
ural size indicated by line.) 
The subfamily Tettiginae includes the strange little Acridiids known as 
“grouse-locusts.” They are all under f inch in length, and most of 
them are less than J inch. They have the wing-covers reduced to mere 
scales, but the pronotum is so long that it extends back over the rest of the 
