The jumping legs of the creature are filled with powerful muscles, which, when they expand, can hurl it through the air and enable it to escape from its enemies. On the inner side of the femur is a musical instrument, a row of hard, bead-like projections, which are very highly developed in the males, but not at all in the females. When one of the veins of the upper wing, which is prominent and has a sharp knife edge, is scraped over these projections, a musical sound is made by the vibration of the whole wing. It would seem to be the case, as with so many of the birds, that only the male can sing, the female being mute. [Illustration] THE KATYDID (_Scudderia sp._) How marvelously equipped such a creature as this is to live! The great eyes, with many facets, enable it to see by night as well as by day. Its long, slender antennæ catch the faintest odor, and probably are sensitive to a host of perfumes that we do not know. In the front of each fore leg, just below the knee, is a dark, sunken area, the ear, with which it can probably hear sounds too faint for our ears, and by moving them can tell from which direction the sounds come. Its long muscular legs enable it to jump a hundred times its length whereas man can scarcely cover three times his length at a leap. Its wings not only enable it to fly well, but in the males are provided with an apparatus near their base for making a musical sound. This sound is made by half opening the long green wings and closing them again rapidly. The left wing bears a file on its inner surface near the base, while the other, the right wing, has a sharp knife edge on the outside just below the file on the left wing. In closing the wings together the knife edge scrapes across the file and makes at least one of the wings vibrate. While the wings are opening no sound is produced; as they close the characteristic sounds so like the words "Katy did" are made. [Illustration] THE NARROW-WINGED KATYDID (_Scudderia sp._) If it is any comfort for sleepless ones to know it, the katydid is one of the noisiest creatures of its size in the world. It is only the males which call their "Katy-did, Katy-didn't, she did, she didn't," and they are calling to their mates. There are people who prefer the noises of the street-cars to the noises of Nature, and who complain that the buzz of insect life on a summer evening makes them feel lonesome and unhappy, but to me half the mystery and charm of tropical life lies in the music of the night insects. Our southern states, with their tropical summers, have a wealth of insect life quite comparable to that of the tropics and vastly more varied than that of northern Europe. The katydid is the greatest songster of this night choir and is a truly American species--as truly a thing to be proud of as the mocking-bird.