Vulnerable Areas on the Surface of the Tarsus and Pretarsus of the Grasshopper (Acrididae, Orthoptera); with Special Reference to the Arolium

Ten or twelve years ago, while studying the effects of dyes on the eggs of the grasshopper, Melanoplus differentialis , the present writer, in an idle moment, immersed a living adult of this species in one of the stains which happened to be on hand—just which one has been forgotten—and left it there for some time. Later, when the animal was removed and washed, the under surface of each arolium was found to be brightly colored; but no other part of the surface of the animal had stained. This seemed interesting and worth further study. Microscopic sections of the arolia were made and found to contain some unusual structures; but other work in progress seemed more pressing and nothing more was done with this at the time.