The New International Encyclopædia/Froth-fly

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FROTH-FLY, FROTH-HOPPER, FROGFLY, or FROGHOPPER. Insects of which the young — larvæ and pupæ — are found in a frothy exudation on plants. They form the family Cercopidæ of homopterous bugs, and are allied to aphids, and still more nearly to cicadas and lantern-flies. The larvæ and pupæ differ little in appearance from the perfect insect, except that the latter possesses four large wings. The froth, commonly called frog-spittle, is believed to be composed of sap which the insect sucks up through its proboscis. The sap passes through the intestine and is emitted as a clear mass, into which the insect draws bubbles of air by means of its tail claspers, and thus makes foam. When the insect is about to transform, the foam dries in such a way as to produce a shelter for the ensuing quiescent stage. The most common one in the Eastern United States is Aphrophora quadrangularis. Some of the tropical forms assume very bizarre shapes, caused by outgrowths from the thorax. The fluid is emitted by some species in drops which may be thrown a considerable distance, causing the phenomenon known as weeping trees. A few dozen larvæ of a Madagascar form may exude a quart of fluid in an hour and a half. Frog-spittle is supposed to be produced as a protective covering for the young insect, but in spite of it certain Hymenoptera pick the larvæ out and carry them off to lie stored as food for their larvæ. The winged stage is a much flattened one and capable of long leaps, whence the name ‘froghopper,’ first given to them because they came from the ‘frog-spittle,’ is doubly appropriate.