Fig. 109.—How a Grasshopper Walks.
Fig. 110.—How a Spider Walks.
The leg of a grasshopper (as of all insects) is said to have five parts, all the small parts after the first four parts being counted as one part and called the foot. Are all the legs similar, that is, do the short and the long joints in all come in the same order? Numbered in order from the body, which joint of the leg is the largest,—the first, second, third, or fourth? Which joint is the shortest? The slenderest? Which joint has a number of sharp points or spines on it? Find by experiment whether these spines are of use in walking (Fig. [106]). Jumping? Climbing? In what order are the legs used in walking? How many legs support the body at each step?
All animals that have ears have ways of communicating by sounds. Why would it be impossible for the grasshopper to have a voice, even if it had vocal cords in its throat? The male grasshoppers of many species make a chirping, or stridulation, by rubbing the wing against the leg. Look on the inner side (why not outer side?) of the largest joint of the hind leg for a row of small spines visible with the aid of a hand lens (Fig. [111]). The sound is produced by the outer wings rubbing against the spines. Have you noticed whether the sound is produced while the insect is still or in motion? Why? The male grasshoppers of some species, instead of having spines, rub the under side of the front wing on the upper side of the hind wing.
Fig. 111.—A, Row Of Spines, z, used in chirping.
B, the same more enlarged.
Wings.—To what is the first pair of wings attached? The second pair? Why are the wings not attached to the prothorax? Why are the wings attached so near the dorsal line of the body? Why are the second and third rings of the thorax more solidly joined than the first and second rings?
