. Principles of economic zoo?logy. Zoology, Economic. HEMIPTERA 143 cannot talk ; The sound is made by " stretching and relaxing a pair of corrugatetl tympana or parchment-like membranes by means of a muscle attached to the center of ;' The strangest freak in all insect life is the periodical cicada or seventeen- year locust (Fig. 113). It is the longest lived of all insects, for while other insects pass from the egg to imago form in a few days or weeks, or, at the most, in one to three years, this insect requires from tliirteen to seven- teen years for this developmen
. Principles of economic zoo?logy. Zoology, Economic. HEMIPTERA 143 cannot talk ; The sound is made by " stretching and relaxing a pair of corrugatetl tympana or parchment-like membranes by means of a muscle attached to the center of ;' The strangest freak in all insect life is the periodical cicada or seventeen- year locust (Fig. 113). It is the longest lived of all insects, for while other insects pass from the egg to imago form in a few days or weeks, or, at the most, in one to three years, this insect requires from tliirteen to seven- teen years for this development. In the spring the female cuts slits in tender twigs and lays her eggs therein. In about six weeks they hatch and the nymphs spend the required seventeen years, or, in the case of a southern form, thirteen years, in the ground. They feed by sucking the juices of tender roots. In the spring of the seventeenth or the thirteenth year—as the case may be—they crawl up to the surface of the ground,. Fig. 113.—The seventeen-year Cicada (c) and pupa (a, b); d, position of eggs (e); /, larva. (Riley.) undergo their last molting, and emerge as clear-winged cicadas. This insect is a fine example of protective resemblance. One may be within a few inches of a " singing " cicada and not be able to see it, so near the color of the tree trunk or ground is it. The adult life is short. They lay their eggs, sing their songs, and die. The plant-lice or aphids {Aphid'idce) are among our most common and destructive pests in the green-house, field, and orchard. There are many species, most of which are small, the largest barely reaching the length of \ inch. The small, soft, usually green body is somewhat pear shaped. Wingless forms are most numerous, but there are forms in almost every brood which have two pairs of dehcate transparent wings, the anterior pair of which is the larger. " The two wings of each side are usually con- 1 Kellogg, p. Please note that these images
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