Insect guide > Cicadas
This is a group of insects commonly known by the popular name of "harvest flies" or cicadas, and frequently in this country by the erroneous term "locust". The term "locusts" should properly be applied to the long-horned grasshoppers of the true family Locustidae, although it is also, especially by British subjects, applied to the short-horned grasshoppers and especially the destructive species.
The family cicadae is a group of large insects containing very many tropical species. Their bodies are large, with a wide, blunt head and with prominent eyes on the outer angles. The head has three ocelli placed triangularly on the summit between the compound eyes and the antennae consist of a short basal joint surmounted by a bristle which is divided into about five segments. The tropical forms are sometimes brightly colored but the species which occur in the United States are usually greenish marked with black.
The commonest form in the more Northern States is the socalled "dog-day harvest fly" or "lineman" - the insect which every summer, toward the end of July or early in August, begins its doleful but resounding buzzing hum in the tree tops. This sound is familiar throughout the hot days of the late summer and is frequently more noticeable in the early morning and about sundown. This, however, may be due to the fact that the day noises of a town or city are less noticeable at such times. It is supposed that this is an annual species, i.e., that it has but one generation annually, the larvae living in the ground through only nine or ten months of the year. It may - that it has a much longer larval period, and that be, however , that it has a much longer larval period, and that only its great abundance and the intermingling of generations accounts for its annual occurrence in the adult condition. More information and cicada pictures.
This is a point which should be investigated as its life history has never been thoroughly worked out. There are other cicadas in the Southern and Western States, some of them rather small in size, like Tettigia hieroglyphica, and others large, like the big Cicada emarginata.
Life History of the "Seventeen-year Locust"
(Cicada septendecim, L.)
This insect, commonly known as the periodical cicada or seventeen-year locust, is taken here because it is the only species of the family whose life history is thoroughly well understood.
It is probably not typical in its very extended larval life. In the North this insect remains either as larva or pupa underground for seventeen years. In the South it develops in thirteen years, thus giving rise to two races which are known as the septendecim and tredecim races. The dividing line between the two races corresponds fairly well with the northern margin of the so-called lower austral life zone. In some localities confusion arises from the fact that the insect makes its appearance at shorter intervals than seventeen years. This is accounted for by the fact that the insect appears in distinct broods some of which overlap the territory also inhabited by other broods. There is no reason, however, to suppose that the length of life of any larva is of shorter duration than seventeen years in the North and thirteen in the South.
It will be found in great numbers throughout New Jersey, Delaware, part of Pennsylvania, Maryland, northern Virginia, Ohio, southern Michigan, Indiana, eastern Illinois, Kentucky and down the Appalachian chain of mountains through North Carolina into northern Georgia. It will also appear in a few localities in Vermont, New York, Wisconsin, West Virginia and Tennessee.
The eggs are laid in small twigs and branches which are pierced by the ovipositor and in this way the insect does practically the only damage which it accomplishes. They occur in enormous swarms and the weakening of the twigs, caused by the punctures, causes many of them to be broken off by the wind. The young ant-like larva hatches from the eggs a few weeds after oviposition, escapes from the wounded limb, falls to the ground and burrows quickly out of sight, where it forms for itself a little underground chamber near some rootlet, remaining there, isolated from others and moving, probably very slowly, for seventeen or thirteen years. It molts four times, the first time after from one year to eighteen months, the second after two additional years, the third after three years more, and the fourth after another period of three or four years, leaving three or four additional years to elapse before the insect assumes the socalled pupal state. The anterior legs of the larva are curiously enlarged and resemble the cutting jaws of biting insects. They are especially designed for digging and transporting earth.
The food which it consumes is obtained probably from the soil humus and to some extent from the roots of plants. After the change to the pupal condition the insect burrows to the top of the ground and, emerging, crawls up the trunks of trees where the skin splits and the adult insect issues. Occasionally, in certain kinds of soil or when the pupa has reached the surface too early, it will construct mud chimneys from the summit of which it eventually issues.