Page:Insects - Their Ways and Means of Living.djvu/259

 PERIODICAL CICADA

downward and slanted toward the door. Generally there are six or seven eggs in each row (E), making twenty-four to twenty-eight eggs in the whole nest, but frequently there are more than this. The wood fibers at the entrance are much frayed by the action of the ovipositor and make a fan-shaped platform in front of the door (A, B, C). Here the young shed their hatching garments on emerging from the nest. The series of cuts in the bark eventually run together into a continuous slit, the edges of which shrink back so that the row of nests comes to have the appearance of being made in a long groove. This mutilation kills many twigs, especially those of oaks and hickories, the former soon showing the attacks of the insects by the dying leaves. The landscape of oak- covered regions thus becomes spotted all over with red- brown patches which often almost cover individual trees from top to bottom. Other trees are not so much injured directly, but the weakened twigs often break in the wind and then hang down and die.

An ovipositing female (Plate 7) finishes each egg nest in about twenty-five minutes; that is, she digs it out and fills it with eggs in this length of rime, for each chamber is filled as it is excavated. A female about to oviposit alights on a twig, moves around to the under surface, and selects a place that suits her. Then, elevating the abdomen, she turns her ovipositor forward out of its sheath and directs its tip perpendicularly against the bark. As the point enters it goes backward, and when in at full length the shaft slants at an angle of about forty-five degrees.

In a number of cases females were frightened away at different stages of their work, and an examination o(the unfinished nests showed that each chamber is filled with eggs as soon as it is excavated; that is, the insect completes one chamber first and fills it with eggs, then digs out the other chamber which in turn receives its quota of eggs, and the whole job is done. The female now moves

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INSECTS