Page:Harper's New Monthly Magazine - v109.djvu/56

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with it! Entomologists have speculated as to the use of these turrets. The writer's opinion is that they were built by pupæ who, for some reason, had miscalculated the time of their exode. They reached the top too soon, halted, and built themselves a temporary refuge, as men and cicadas who are "ahead of their time" must commonly do, or die.

There are few things in nature more wonderful than the common impulse which seizes these millions of undeveloped insects living in dark tunnels underneath the ground and urges them to cut their way upward, that they may complete their appointed life in the upper air. Stirred by this strange unrest, the mighty host begins to move. What engineering skill directs their course aloft? What instinct guides their movements and enables them with unerring accuracy to burrow to the sunlight? If we suppose that a pupa reaches the surface before it is quite prepared to transform, or, when the surface is reached, that weather or other conditions retard the change to the winged form, we have the influences that require it to build a shelter. Its manner of proceeding is interesting and ingenious. It brings up from its burrow a little ball of mud, which it carries between its mouth and strong forepaws. The latter are admirably designed for digging. The pellets are placed atop of one another, as a mason would lay stones while building a circular tower. They are moistened by saliva, which serves as a sort of cement, and are pushed down upon each other by the head and feet, and thus adhere tenaciously. The inside is smoothed by continued motion of the jaws, as a plasterer spreads mortar upon a wall. It is not varnished, however,