70 THE PERIODICAL CICADA. 
THE ACT OF TRANSFORMATION. 
The phenomenon connected with the transformation of the periodical 
Cicada from the pupal to the adult stage is a very interesting one and 
always fills the observer with considerable wonderment. As remarked 
by Mr. Butler, when these iusects emerge from the ground it is usually 
with a rush, and a lively scramble ensues for each elevation near the 
point of their emergence. Trees, bashes, weeds, poles, stumps, fences; 
in fact, everything upon which they can get above the level of their 
recent homes is ascended. The instinct which has caused them to 
burrow to the surface of the ground still drives them in the same direc- 
tion upward, and they seem to make up for their long subterranean 
periods and their weeks of waiting near the surface in activity when 
the time has finally arrived for their emergence. The different steps 
undergone by the insects in transforming from the pupal to the adult 
stage have been perhaps most acccnrately described by Professor Riley, 
as given below. 1 The plate accompanying his description is reproduced 
in this bulletin as a frontispiece. 
The unanimity with which all those which rise within a certain radius of a given 
tree crawl in a hee line to the trunk of that tree is most interesting. To witness 
these pupae in such vast numbers that one can not step on the ground without crush- 
ing several swarming our of their subterranean holes and scrambling over the 
ground, all convergiug to the one central point, and then in a steady stream clam- 
bering up the trunk and diverging again on the branches, is an experience not 
readily forgotten and affording good food for speculation on the nature of instinct. 
The phenomenon is most satisfactorily witnessed where there is a solitary or isolated 
tree. 
The pupae (frontispiece, figs. 1 and 2) begin to rise as soon as the sun is hidden 
behind the horizon, and they continue until by 9 o'clock the bulk of them have 
risen. A few stragglers continue until midnight. They instinctively crawl along 
the horizontal branches after they have ascended the trunk and fasten themselves 
in any position, but preferably in a horizontal position on the leaves and twigs of 
the lowermost branches. In about an hour after rising and settling the skin splits 
down the middle of the thorax from the base of the clypeus to the base of the 
metanotum (frontispiece, Q^. 3), and the forming Cicada begins to issue. * * * 
The colors of the forming Cicada are a creamy white, with the exception of the 
reddish eyes, the two strongly contrasting black patches on the prothorax, a black 
dash on each of the coxae and sometimes on the front femora, and an orange tinge at 
the base of wings. 
There are five marked positions or phases in this act of evolving from the pupa 
shell, viz, the straight or extended, the hanging or head downward, the clinging or 
head upward, the flat winged, and, finally, the roof winged. In about three min- 
utes after the shell splits the forming imago extends from the rent almost on the 
same plane with the pupa, with all its members straight and still hold by their tips 
within the exuvium (frontispiece, fig. 4). The imago then gradually bends back- 
ward and the members are loosened and separated. With the tip of the abdomen 
held within the exuvium, the rest of the body hangs extended at right angles from 
it, and remains in this position from ten to thirty seconds or more, the wing pads 
separating, and the front pair stretching at right angles from the body and obliquely 
crossing the hind pair (frontispiece, figs. 5 and 6). They then gradually swell, and 
1 Annual Kept. Dept. of Agriculture, 1885, pp. 237, 238. 
