The Birth of a Cicada.
A. Hyatt Verrill
Although most of our readers of Popular Science News are no doubt familiar with the life-history of our common cicada, or "locust" as it is commonly called, I doubt if many of them have actually witnessed the metamorphosis of this extremely interesting insect taking place. The expected appearance of one of the periodical plagues of this insect next year, adds interest to the subject. It was recently my good fortune to observe this birth, as it may be termed, and even more fortunate was the fact that I was enabled to secure a series of unique photographs of the different stages of the transition, which with those of the adult and a few others obtained at various times, form a complete series of pictures, portraying practically the life-history of the species from pupa to adult.
As is well-known, the grubs or larvae of the cicada, as soon as hatched from the eggs,—which are laid in slits in twigs or fruit,—at once descend to the earth and bury themselves beneath the surface. Here they remain for a period of two years, in the case of our common species, or seventeen years in the case of the "seventeen-year locust." During this time the nymphs subsist on the sap and juices of roots, until, when fully grown, they come forth from the ground, and, clinging to some nearby object,—as a tree or fence-post,—shed the skin and emerge as full-grown, winged sap-suckers. Although the strident song is familiar to everyone and the cast-off nymph skins are abundant throughout the summer, the adults are comparatively seldom seen; and, as the metamorphosis takes place early in the morning, few observe it. This is still further accounted for by the surprising fact that the entire operation of shedding the cast-off skin, from the time the dorsal crack appears until the wings are completely dried and flight takes place, occupies only about half an hour.
The grub on which my observations were made was a large, healthy specimen, and was captured just as he came from the ground. This was at 10.05 A.M. He was immediately placed on a stiff hickory twig where he apparently felt perfectly at home, but wandered aimlessly about for some time. This uneasiness was, I think, due to the fact that he had emerged from his earthy exile a little ahead of time, the earth in his vicinity having been disturbed the day previous.
At 12.30 he was observed to be motionless, resting against the twig, and an examination showed his hooked foot rigidly fixed in the minute crevices of the bark. At this time, however, he showed no hesitation in changing his location when disturbed, but almost immediately resumed his rigidity. At 1.05 p.m. a slight shiver was observed to run through his body and instantly the skin along the dorsal, median line, cracked open. For three minutes this crack increased but very little in width and not at all in length. At 1.10, however, the crack rapidly began to increase in size, and the head of the cicada was visible in the opening. The head steadily pushed forward with apparently no voluntary motion until at 1.15 the head and about half the thorax protruded from the pupa case.
At this time the nymph-skin became overbalanced and loosened from the support, and if left to itself would undoubtedly have fallen. It was carefully replaced and the now lifeless claws hooked readily into the bark of the supporting twig.
The motion of the emerging insect was a steady, gliding, slightly twisting movement, but the insect itself showed no sign of life or voluntary muscular motion until 1:17. At this time the fore-legs were free and groped about feebly. The wing pads next appeared and were slightly raised. The second pair of legs followed, and the cicada now bent slowly forward and downward until the free feet grasped the twig. The movement, however, dislodged the pupa again, and it was found necessary to place it in a slightly different position where the emerging creature could more readily grasp a support.
At 1:18 the cicada was entirely free with the exception of the posterior portion of the abdomen and the third pair of legs. The first two pairs of legs now seized the twig, and, after a brief moment of rest, the body was pulled rather jerkily free from the old skin and the new-born cicada was free at last. He now travelled steadily upward to the extremity of the twig, where he arrived at 1:21 p.m. Upon reaching this point of vantage the wings were lifted and waved slowly back and forth, much in the manner of a newly-emerged butterfly. At the same time the front legs were run over the proboscis, smoothing and drying it.
The motion of the wings continued steadily, and as the thorax and abdomen dried the soft, powdery down appeared on the body. At 1:24 the wings had attained their full size but still remained soft and pliable. At 1:26 the posterior wings were apparently satisfactory to their owner and were placed motionless along the back. The anterior wings were kept moving, however, until 1:31, when they were also folded in place. The insect now busied himself with his first toilet, rubbing his legs, cleansing his mouth-parts and head and frequently lifting his entire weight, as if trying his strength. At 1:34 everything was accomplished and with evident desire to see more of the world the wings were spread and the new arrival took flight.