(_Dissosteira carolina_, Linn.) If you raise the wing of a full-grown grasshopper and look behind its big fat thigh, you will see a strange hole into its body. This is supposed to be its ear, but what it hears and what it does not hear, who can tell? When on a warm summer day you hear a male grasshopper chirping, for the males alone can sing, you can think that somewhere nearby, perhaps with wings lifted to hear the song better, sits some attentive female whose ears are tuned to catch the plaintiveness of this courting song. [Illustration] THE GRASSHOPPER'S HEARING ORGAN (_Dissosteira carolina_, Linn.) As we grow older and certain sounds which we heard in childhood with the greatest ease become harder for us to hear and are finally lost to as altogether, we begin to appreciate the relative character of sound. Some boys can hear the faintest twitter of the shyest song bird in the tree tops, while others strain their ears in vain to catch its note. Is it any wonder then that men should be puzzled to know just what the true grasshopper hears? They know there are males of certain species which sing so loud they make our ears ache, but there are others whose noises, if they make any, have never yet been heard by human ears, and yet they all have these ears. They believe, too, that there are certain sounds the grasshopper can hear without the use of these special ears. So whether this strange organ furnishes a special means by which the males and females find each other or not, and what part it has played throughout the centuries in the development of this marvelous form of living matter, are things that man may be a long time yet in finding out. In the photograph it lies to the left, a dark kidney-shaped opening with the ear drum membrane at an angle just inside its rim. It has a well-formed tympanum, and nerves and muscles of a complex nature. [Illustration] THE SHORT-WINGED GREEN LOCUST (_Dicromorpha viridis_, Scudd.) Whether this creature has a personality or not may be forever extremely difficult for humans to decide. Its eyes that look like cows' eyes really cast hundreds of images on a special kind of brain, so different from our own that we cannot understand it, and then, besides these great big eyes, it has three others scarcely visible in the picture. Its short-ringed horns are not horns at all, but sense organs of so complicated a nature that we do not yet know certainly whether they are organs of smell or not, and it is supposed that they may be the seat of sense organs that we humans do not have.