any jumping, orthopterous insect, of the families acrididae and locustidae. the species and genera are very numerous.  the former family includes the western grasshopper or locust (caloptenus spretus), noted for the great extent of its ravages in the region beyond the mississippi. in the eastern united states the red-legged (caloptenus femurrubrum and c. atlanis) are closely related species, but their ravages are less important. they are closely related to the migratory locusts of the old world. see locust.-in ordinary square or upright pianos of london make, the escapement lever or jack, so made that it can be taken out and replaced with the key; -- called also the hopper.