ECAUSE the grasshopper affords special facilities for the study of insect structure, it has indeed become a burden to the students in the laboratories of American universities. But in nature-study we must not make anything a burden, least of all the grasshopper, which being such a famous jumper as well as flier, does not long voluntarily burden any object.
Since we naturally select the most salient characteristic of a creature to present first to young pupils, we naturally begin this lesson with the peculiarity which makes this insect a "grasshopper." When any creature has unusually strong hind legs, we may be sure it is a jumper, and the grasshopper shows this peculiarity at first glance. The front legs are short, the middle legs a trifle longer, but the femur of the hind leg is nearly as long as the entire body, and contains many powerful muscles which have the appearance of being braided, because of the way they are attached to the skeleton of the leg; the tibia of the hind leg is long and as stiff as if made of steel. When getting ready to jump the grasshopper lowers the great femur below the level of the closed wings and until the tibia is parallel with it and the entire foot is pressed against the ground. The pair of double spines at the end of the tibia, just back of the foot, are pressed against the ground like a spiked heel, and the whole attitude of the insect is tense. Then, like a steel spring, the long legs straighten and the insect is propelled high into the air and far away. This is a remarkable example of insect dynamics; and since so many species of birds feed upon the grasshopper, its leaping power is much needed to escape them. However, when the grasshopper makes a journey it uses its wings.
As we watch a grasshopper crawling up the side of a vial or tumbler we can examine its feet with a lens. Between and in front of the claws is an oval pad which clings to the glass, not by air pressure as was once supposed, but by means of microscopic hairs, called tenent hairs, which secrete a sticky fluid. Each foot consists of three segments and a claw; when the insect is quiet, the entire foot rests upon the ground; but when climbing on glass, the toe pads are used.
The grasshopper's face has a droll expression; would that some caricaturist could analyze it! It is a long face, and the compound eyes placed high upon it, give a look of solemnity. The simple eyes can be made out with a lens. There is one just in front of each big eye, and another, like the naughty little girl's curl, is "right in the middle of the forehead." The antennæ are short but alert. The two pairs of palpi connected with the mouth-parts are easily seen, likewise the two pairs of jaws, the notched mandibles looking like a pair of nippers. We can see these jaws much better when the insect is eating, which act is done methodically. First, it begins at one edge of a leaf, which it seizes between the front feet so as to hold it firm; it eats by reaching up and cutting downwards, making an even-edged, long hole on the leaf margin; the hole is made deeper by repeating the process. It sometimes makes a hole in the middle of a leaf and bites in any direction, but it prefers to move the jaws downward. While it is feeding, its palpi tap the leaf continually and its whole attitude is one of deep satisfaction. There is an uprolled expression to the compound eyes which reminds us of the way a child looks over the upper edge of its cup while drinking milk. The grasshopper has a preference for tender herbage, but in time of drouth will eat almost any living plant.
Back of the head is a sun-bonnet-shaped piece, bent down at the sides, forming a cover for the thorax. The grasshopper has excellent wings, as efficient as its legs; the upper pair are merely strong, thick, membranous covers, bending down at the sides so as to protect the under wings; these wing-covers are not meant for flying and are held stiff and straight up in the air, during flight. The true wings, when the grasshopper is at rest, are folded lengthwise like a fan beneath the wing-covers; they are strongly veined and circular in shape, giving much surface for beating the air. The grasshoppers' flight is usually swift and short; but in years of famine they fly high in the air and for long distances, a fact recorded in the Bible regarding the plague of locusts. When they thus appear in vast hordes, they destroy all the vegetation in the region where they settle.
The wings of grasshoppers vary in color, those of the red-legged species being gray, while those of the Carolina locusts are black with yellow edges. The abdomen is segmented, as in all insects, and along the lower side there are two lengthwise sutures or creases which open and shut bellows-like, when the grasshopper breathes. The spiracles or breathing pores can be seen on each segment, just above this suture.
The grasshopper has its ears well protected; to find them, we must lift the wings in order to see the two large sounding disks, one on each side of the first segment of the abdomen. These are larger and much more like ears than are the little ears in the elbows of the katydids.
The singing of the short-horned grasshoppers is a varied performance, each species doing it in its own way. One species makes a most seductive little note by placing the femur and tibia of the hind legs together, and with the hind feet completely off the ground, the legs are moved up and down with great rapidity, giving off a little purr. The wings in this case, do not lift at all. There are other species that make the sound by rubbing the legs against the wing-covers.
The grasshopper makes its toilet thus: It cleans first the hind feet by rubbing them together and also by reaching back and scrubbing them with the middle feet; the big hind femur it polishes with the bent elbow of the second pair of legs. It cleans the middle feet by nibbling and licking them, bending the head far beneath the body in order to do it. It polishes its eyes and face with the front feet, stopping to lick them clean between whiles, and it has a most comical manner of cleaning its antennæ; this is accomplished by tipping the head sidewise, and bending it down so that the antenna of one side rests upon the floor; it then plants the front foot of that side firmly upon the antenna and pulls it slowly backward between the foot and floor.
The grasshopper has some means of defence as well as of escape; it can give a painful nip with its mandibles; and when seized, it emits copiously from the mouth a brownish liquid which is acrid and ill-smelling. This performance interests children, who are wont to seize the insect by its jumping legs and hold it up, commanding it to "chew tobacco."
Grasshoppers are insects with incomplete metamorphosis, which merely means that the baby grasshopper, as soon as it emerges from the egg, is similar in form to its parent except that it has a very large head and a funny little body, and that it has no quiet stage during life. When immature, the under wings or true wings have a position outside of the wing-covers and look like little fans.
The short-horned grasshoppers lay their eggs in oval masses protected by a tough overcoat. The ovipositor of the mother grasshopper is a very efficient tool, and with it she makes a deep hole in the ground, or sometimes in fence rails or other decaying wood; after placing her eggs in such a cavity, she covers the hiding place with a gummy substance so that no intruders or robbers may work harm to her progeny. Most species of grasshoppers pass the winter in the egg stage; but sometimes we find in early spring the young ones which hatched in the fall, and they seem as spry as if they had not been frozen stiff.
The Red-Legged Grasshopper
Leading thought—The grasshopper feeds upon grass and other herbage and is especially fitted for living in grassy fields. Its color protects it from being seen by its enemies the birds. If attacked, it escapes by long jumps and by flight. It can make long journeys on the wing.
Method—The red-legged grasshopper (M. femur-rubrum) has been selected for this lesson because it is the most common of all grasshoppers, though other species may be used as well. The red-legged locust, or grasshopper has, as is indicated by its name, the large femur of the hind legs reddish in color. Place the grasshopper under a tumbler and upon a spray of fresh herbage, and allow the pupils to observe it at leisure. It might be well to keep some of the grasshoppers in a cage similar to that described for crickets. When studying the feet, or other parts of the insect requiring close scrutiny, the grasshopper should be placed in a vial so that it may be passed around and observed with a lens. Give the questions a few at a time, and encourage the pupils to study these insects in the field.
1. Since a grasshopper is such a high jumper, discover if you can how he does this "event." Which pair of legs is the longest? Which the shortest? How long are the femur and tibia of the hind leg compared with the body? What do you think gives the braided appearance to the surface of the hind femur? What is there peculiar about the hind femur? Note the spines at the end of the tibia just behind the foot.
2. Watch the grasshopper prepare to jump and describe the process. How do you think it manages to throw itself so far? If a man were as good a jumper as a grasshopper in comparison to his size, he could jump 300 feet high or 500 feet in distance. Why do you think the grasshopper needs to jump so far?
3. As the grasshopper climbs up the side of a tumbler or vial, look at its feet through a lens and describe them. How many segments are there? Describe the claws. How does it cling to the glass? Describe the little pad between the claws.
4. Look the grasshopper in the face. Where are the compound eyes situated? Can you see the tiny simple eyes like mere dots? How many are there? Where are they? How long are the antennæ? For what are they used?
5. How does a grasshopper eat? Do the jaws move up and down or sidewise? What does the grasshopper eat? How many pairs of palpi can you see connected with the mouth-parts? How are these used when the insect is eating? When there are many grasshoppers, what happens to the crops?
6. What do you see just back of the grasshopper's head, when looked at from above?
7. Can the grasshopper fly as well as jump? How many pairs of wings has it? Does it use the first pair of wings to fly with? How does it hold them when flying? Where is the lower or hind pair of wings when the grasshopper is walking? How do they differ in shape from the front wings?
8. Note the abdomen. It is made of many rings or segments. Are these rings continuous around the entire body? Where do their breaks occur? Describe the movement of the abdomen as the insect breathes. Can you see the spiracles or breathing pores? Lift the wings, and find the ear on the first segment of the abdomen.
9. If you seize the grasshopper how does it show that it is offended?
10. How does the grasshopper perform its toilet? Describe how it cleans its antennæ, face and legs.
11. What becomes of the grasshoppers in the winter? Where are the eggs laid? How can you tell a young from a full-grown grasshopper?
12. Do all grasshoppers have antennæ shorter than half the length of their bodies? Do some have antennæ longer than their bodies? Where are the long-horned grasshoppers found? Describe how they resemble the katydids in the way they make music and in the position of their ears.
Supplementary reading—Chapters XVI-XVIII in Grasshopper Land, Morley.