SEVENTEEN-YEAR CICADA.
Adult, Chrysalis-Case, Pupa, Entrances to Burrows and Egg-Nests.
About the middle of June the perfect insects make their appearance, and as they generally come in large numbers they do a great deal of damage. In some localities they congregate to such an extent upon the trees as to bend and even to break down the limbs by their weight. The din of their discordant drums resounds in the woods and orchards from morning to evening. As their life is of rather short duration, not lasting for a longer period than a month, they soon begin to pair, and it is not long afterwards that the females may be seen preparing nests for the reception of their eggs. Branches of moderate size are selected for this purpose. Their manner of perforation is curious and interesting. Clasping the branch on both sides with their legs, and bending the ovipositor at an angle of forty-five degrees, they repeatedly thrust it into the bark and wood in the direction of the fibres, at the same time setting the lateral saws at work, thereby detaching little splinters of wood at one end, which are intended to serve as a kind of fibrous cover for the nest. The hole is bored obliquely to the pith, and by a repetition of the same operation is gradually enlarged until is formed a longitudinal fissure of sufficient extent to receive from ten to twenty eggs. The side-pieces of the piercer act as a groove to convey the eggs to the nest, where they are deposited in pairs, but separated from each other by a narrow strip of wood. When two eggs have been thus placed, the piercer is withdrawn for a moment, and then inserted till two more eggs are dropped in a line with the first, and thus the operation is repeated until the fissure has been filled, when the insect removes to a little distance and commences to make another nest to contain two more rows of eggs. It takes about fifteen minutes to prepare a groove and fill it with eggs. As many as twenty grooves are sometimes made in a branch by a single insect, and when the limb has been sufficiently stocked she goes from it to another, or from tree to tree, until she has got rid of her complement of from five hundred to seven hundred eggs. So weak does she at length become, in her continued endeavor to provide for the succession of her race, as to fall, in an attempt to fly, an almost lifeless lump to the earth, where her spirit soon goes out never more to enliven its frail house of clay.
Although Cicadas abound most upon the oaks, yet there seem to be no trees or shrubs that are exempt from their attacks, unless it be the various species of pines and firs. The punctured limbs languish and die soon after the eggs are laid, and as often happens are broken off by the winds; but when this is the case the eggs never hatch, for the moisture of the living branch seems necessary for their proper development.
The eggs are one-twelfth of an inch in length, and one-sixteenth of an inch through the middle, but taper to an obtuse point at each end. They are of a pearl-white color. The shell is so thin and delicate that the form of the inclosed insect can be seen before the egg is hatched. One writer claims that fifty-two days, and others that fourteen days, constitute the period required for the hatching of the egg.
When it bursts the shell the young insect is one-sixteenth of an inch long, and is of a yellowish-white color, excepting the eyes and the claws of the fore-legs, which are reddish. It is clothed with small hairs. In form it is grub-like, larger proportionally than the parent, and provided with six legs, the first pair being very large, shaped like lobster-claws, and armed beneath with strong spines. Little prominences take the place of wings, and under the breast is a long beak for suction. Its movements, after leaving the egg, are very lively, and nearly as quick as some of the ants. But after a few moments their instincts prompt them to reach the ground. They do not attain this end by descending the body of the tree, nor by casting themselves off precipitately, but, running to the side of the limb, deliberately loosen their hold and drop to the ground, making the perilous descent with the utmost safety. This seems almost incredible, but it has been repeatedly observed by scores of honest witnesses.
NEW-BORN CICADA.
Line Below Shows Natural Size.
On reaching the ground the young insects immediately burrow their way into the soil, using their broad and strong fore-feet pretty much after the fashion of the mole. They apparently follow, in their descent, the roots of plants, fastening their beaks into the most tender and succulent, and thus imbibing their juices, which constitute their sole aliment. They do not descend very deeply into the ground, probably not more than ten or twelve inches, although accounts have been published of their discovery at a depth of ten or twelve feet, but their occurrence at such great distances from the top of the ground is doubtless the result of accident.
The only alteration to which the insects are subject during the seventeen years of their subterranean confinement, is an increase in size, and the more complete development of the four small scale-like prominences of the back, which contain their future wings.