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Page:Popular Science Monthly Volume 57.djvu/38

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POPULAR SCIENCE MONTHLY.

will crawl about the table or even on the dusty floor and live for an hour or two in this condition. The usually glabrous surface of the body, however, becomes shriveled after a while. On the other hand, it immediately sinks in water, and will live for some time immersed in this way, and this leads me to believe that the appendages above described may perform a slight respiratory function. The fact that the insect immediately sinks may be cited as an additional evidence that it does not emit air.

It is interesting to observe that regarding this stage of Aphrophora as an aquatic stage, since it lives immersed in fluid, we have the same behavior that we observe in the aquatic stages of other Hemiptera, as well as in insects of other orders. The great water beetle Hydrophilus has an aquatic larva. Myall, quoting Lyonet, says: "They never remain long at the bottom of the water; air is necessary for them, and this they take in by the tail, which they raise from time to time to the surface of the water." In the larva of Dysticus, another water beetle, the only functional spiracles are the last pair, opening at the tail. The little oval beetles, known as whirligigs, from their rapid whirling motion, when swimming on the surface of the water carry down a bubble of air on the end of the abdomen, and when this has been exhausted in the process of respiration rise to the surface for a fresh bubble. The larvæ of some forms are furnished on each side with long respiratory filaments.

A number of neuropterous insects whose early stages are passed in the water are furnished with branchial tracheæ or false gills. These consist of filaments springing from the sides of the abdominal segments. In the early stages of certain dragon flies the rectum supports epithelial folds which are filled with fine tubes from the tracheal system. Among certain aquatic insects belonging to the order of Hemiptera the creatures reach out the hinder portion of the body to secure air. Dr. Myall, in his very interesting book on the Natural History of Aquatic Insects, says: "A Nepa or a Ranatra may sometimes be seen to creep backward along a submerged weed until the tip of its breathing tube breaks the surface of the water."

The Aphrophora while immersed in the watery fluid, whether secreted by itself or consisting of clear water which has been supplied to it, reaches out for air in a precisely similar manner. Primarily the froth made by this insect not only keeps the body moist, but acts as a protection against its enemies.

A number of individuals may often be found in one fleck of froth, and they are entirely hidden from sight while immersed in this way. The viscid character of the fluid secreted insures the retention of the air the insect collects in the form of little