Page:Insects - Their Ways and Means of Living.djvu/226



Bulletin, Tte Periodical Cicada, published by the United States Bureau of Entomology in I9O 7. Doctor Marlatt describes six immature stages of the periodical cicada between the egg and the adult. The young cicada that first enters the ground is a minute, soft-bodied, pale-skinned creature about a twelfth of an inch in length (Fig. 126). The body is cylindrical and is supported on two pairs of legs, the front legs being the digging organs; the somewhat elongate head bears a pair of small dark eyes and two slender, jointed antennae. At no stage has the cicada _jaws like those of the grass- hopper; it is a sucking insect, related to the aphids, and is provided with a beak arising from the under surface of the head, but when not in use the beak is turned back- ward between the bases of the front legs. Throughout the period of its underground life, the cicada subsists on the sap of roots. During more than a vear the young cicada retains ap- proximately the form it'has at hatching, though the body changes somewhat in shape, principally by an increase in the size of the abdomen (Fig. 13). According to Doctor Marlatt, a nymph of the seventeen-year race first

Fro. 113. Nymph of the periodi- cal cicada in the first stage, about  8 months old, enlarged  5 rimes. (From Marlatt)

sheds its skin, or molts, some- rime during the first two or three months of the second vear of its lire. In its second stage it be- comes a little larger and is marked by a change in the structure of the front legs, the terminal foot part of each being reduced to a mere spur and the fourth section being developed into

a strong, sharp-pointed pick which forms a more efficient organ for digging. The second stage lasts nearly two years; then the creature molts again and enters its th}rd

1861

THE