XXIII. THE GRASSHOPPERS AND LOCUSTS
These forms may be considered the musicians of the insect world. None of the insects can produce vocal sounds, that is, they have no voice, but they have certain appliances which enable them to produce sounds which can be heard a long distance. On hot days in summer is heard the constant and shrill zee-zeeing of the locust, while countless varieties lend their aid in producing a volume of sound.
Fig. 195.—A grasshopper.
The "instruments" in the locust are (Fig. 196) minute teeth, arranged along the thighs; these are rubbed against the fore wings, producing the remarkable sounds. The locusts are commonly called grasshoppers. They have two pairs of net-veined wings, and hind legs adapted for leaping, by which they send themselves sprawling through the air, almost invariably using this method of escape instead of unfolding their delicate wings. All are mimics. The common ground locust resembles the dusty road and the dried foliage which it affects. Others, which live on plants, are a vivid green. Some which I find in my garden resemble closely the tender shoots of the passion vine, upon which they feed.
Fig. 196.—Musical instruments of the locust: a, leg; b, c, teeth, enlarged.
The locusts (Acridiidæ) have short antennæ, large glassy eyes, and ears at the base of the abdomen. The female is provided with an appliance called the ovipositor, four sharp points with which the grasshopper digs holes in the ground; later these are used as a guide or funnel for introducing the eggs into the burrow. The mouth is supplied with parts adapted to biting. When a grasshopper (Fig. 195) is caught it exudes a peculiar fluid resembling molasses, a secretion of the salivary glands. The eggs are deposited in masses from sixty to one hundred. The young resemble the parent, but at first have no wings. The grasshopper in making its metamorphosis, or change from one stage to another, casts its skin in a manner calling to mind the crabs; in a word, it molts several times (Fig. 197). In accomplishing this, it often climbs a spear of grass and there shuffles out of its old skin and jumps away, leaving the hollow skin clinging to the grass.
Fig. 197.—A grasshopper and young at different stages: A, larva; B, pupa; C, adult.
At times they appear in vast numbers, and in clouds rise into the air, so that from a distance they might be taken for smoke or a tornado. This cloud is made up of starving locusts which devastate the countries they infest. They alight upon a wheat field, and an hour later hundreds of acres appear as though a fire had swept over the ground. Every spear of grass, every leaf, has been devoured by this insatiate throng, which can not be destroyed or even checked. In Africa swarms have been swept by the wind out over the ocean, to be washed in in such vast numbers that they formed a line fifty miles long and three or four feet high alongshore, creating an odor which drove people from that region. Jægar, the naturalist, rode through a swarm in Russia for four hundred miles where they were two feet deep. The entire country was devastated by this band of locusts, and tens of thousands of human beings were threatened with starvation. The government troops were ordered to the place and warfare declared against the locusts, the soldiers being armed with shovels instead of guns. A line of thirty thousand men moved slowly forward, covering the insects with earth or digging them under, while in various localities huge fires were built to burn the ground and destroy the eggs. Despite this, thirty thousand people starved to death, the direct result of their raids. Almost every portion of the world away from the poles has been threatened by these raiders. There are many references in the Bible to these insects, and their ravages have been carried on from the earliest times known to man. In America the Rocky Mountain locust is the most destructive, and many of the Western states have been ravaged by them.
"Onward they came, a dark, continuous cloud of congregated myriads, numberless.
The rushing of whose wings was as the sound of a broad river, headlong in its course.
Plunged from a mountain summit, or the roar of a wild ocean, as the autumn storm,
Shattering its billows on a shore of rocks."
—Southey.
Some years ago a flock settled in Colorado Springs, the streets and roofs being covered with them, so that they were swept and shoveled about like snow. Some American swarms have been traced for several hundred miles, and settling on railroads, have stopped the trains by making the tracks slippery. Alighting in a cornfield the rustling sound of their depredation can be heard for some distance; and when they rise, a fire might have swept over the fields, so far as appearances go. The swarm, a black, portentous cloud, sweeps on, flying at a rate of thirty miles an hour to reach some new field, where they dig burrows with their curious ovipositors, and deposit their eggs by millions. Then they move on, leaving an unborn swarm to develop and later constitute another army to spread devastation abroad in the land.
Fig. 198.—Crickets.
The crickets (Fig. 198) are familiar forms with cylindrical bodies and large heads placed vertically, the ovipositor often being as large as the entire body. The female often deposits three hundred eggs in the ground. The note of the cricket is produced by the male, and is a decidedly musical chirp, varying in the different kinds. The close observer may easily find the cave house of the little singer that is often seen sitting at the entrance, singing, not at the top of its voice, but with the full force of its wings, the sound being produced by using the fore wings, as bows and the hind wings as fiddles, and sawing with great rapidity.
The crickets are found in the greatest variety. Some live in the ground, others affect houses, and in the tropics beautiful tree crickets are found. The snowy tree cricket has a peculiar note, te-reat, te-reat, te-reat. The broad-winged tree cricket has a call which resembles a dog whistle. Another has a piping note resembling the thrilling musical sound made by rubbing the edge of a glass with one's finger. The singular cave cricket is wingless, and has antennæ several times the length of its body. The Western cricket does great damage to the crops of the farmer, and when bands are seen marching over the country, ditches are often dug into which the crickets plunge, where, in default of food, they begin to devour one another. The cry of this cricket is harsh and disagreeable, the "musical instrument" being on the dorsum or back of the shield which seems to cover the fore part of its back. The curious mole cricket, which burrows underground and is provided with enormous jaws, is a menace to the gardener. In the outer Florida Keys I found that it was almost impossible to rear plants, so plentiful and ravenous were these fierce root eaters.