520 



SCIENCE. 



[Vol. V., No. 125. 



and bent tibiae are rubbed over the clypeus, 

 the numerous stiff hairs on which act like a 

 comb or a brush in freeing the spine of dirt. 



As the time approaches for the issuing of 

 the pupa, it gradually rises nearer and nearer 

 to the surface ; and, for a year or two before 

 the appearance of any given brood, the pupa 

 may be dug up within one or two feet of the 

 surface. 



In the year of their ascent, from the time 

 the frost leaves the ground, they are found 

 close to the surface, and also under logs and 

 stones, seeming to await the opportune mo- 

 ment, and apparently without feeding. They 

 begin to rise from about the 20th of May in 

 more southern localities, and but little later 

 farther north. In Washington, the present year, 

 they began to rise in scanty numbers about the 

 23d, and were perhaps most numerously rising 

 on the night of the 27th. Those in the city 

 were somewhat earlier than those in the woods 

 just over on the Virginia side. The unanimity 

 with which all those which rise within a certain 

 radius of a given tree crawl in a bee-line to 

 the trunk of that tree, is most interesting. To 

 witness these pupae in such vast numbers that 

 one cannot step on the ground without crush- 

 ing several, swarming out of their subterranean 

 holes and scrambling over the ground, all con- 

 verging to the one central point, and then in 

 a stead}" stream clambering up the trunk, and 

 diverging again on the branches, is an experi- 

 ence not readily forgotten, and affording good 

 food for speculation on the nature of instinct. 

 The phenomenon is most satisfactorily wit- 

 nessed where there is a solitary or isolated 

 tree. 



The pupae begin to rise as soon as the sun is 

 hidden behind the horizon, and the} 7 continue, 

 until, by nine o'clock, the bulk of them have 

 risen. A few stragglers continue until mid- 

 night. They instinctively crawl along the 

 horizontal branches after they have ascended 

 the trunk, and fasten themselves in any posi- 

 tion, but preferably in a horizontal position on 

 the leaves and twigs. 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, and 

 the forming cicada issues. Ecdysis is always 

 an interesting phenomenon, and, when closely 

 watched in our cicada, cannot fail to entertain. 



There are five marked positions or phases in 

 this act of evolving from the pupa-shell; A 7 iz., 

 the straight or extended, the hanging head 

 downward, the clinging head upward, the flat- 

 winged, and, finally, the roof-winged. In about 

 three minutes 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 held by their tips within the 

 exuvium. The imago then gradually bends 

 backwards, and the members are all 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 min- 

 utes or more, the wing-pads separating, and 

 the front pair stretching at right angles from 

 the body, and obliquely crossing the hind pair. 

 They then gradually swell, crimp, and curl, 

 until they form a more or less perfect loop ; 

 and during all this time the legs are becoming 

 firmer, and assuming the natural positions. 

 Suddenly the imago bends upward with a great 

 deal of effort, and, clinging with its legs to the 

 first object reached, — whether leaf, twig, or its 

 own shell, — withdraws entirely from the ex- 

 uvium, and hangs for the first time with its 

 head up. Now the wings perceptibly swell 

 and expand, until they are fully stretched, and 

 hang flatly over the back, perfectly transparent 

 with beautiful white veining. As they dry, 

 they assume the roofed position, and during 

 the night the natural colors of the species are 

 gradually assumed. 



The time required in the transformation va- 

 ries ; and though from the splitting of the skin, 

 and the full stretching of the wings in the flat 

 position, the time is usually about twenty min- 

 utes, it may be, under precisely similar condi- 

 tions, five or six times as long. But there are 

 few more beautiful sights than to see this fresh- 

 forming cicada in all the different positions, 

 clinging and clustering in great numbers to the 

 outside lower leaves and branches of a large 

 tree. In the moonlight, such a tree looks for 

 all the world as though it were full of beautiful 

 white blossoms in various stages of expansion. 



That this insect, in its distribution and in 

 its numbers, has been and is being seriously 

 affected by our civilization, must be apparent 

 to ever} 7 observer. The records show that the 

 numbers have decreased in the successive ap- 

 pearances of certain broods, owing largely to 

 the presence of our domestic animals in the 

 woods. Then, again, the clearing of land and 

 the building of towns and cities have all had 

 their effect upon the decrease of this cicada. 

 There are doubtless many places in Brooklyn, 

 N.Y., where the insect appeared seventeen 

 years ago, in which there will be none the 

 present year. And similarly, I believe that 

 whereas around every tree that has been 

 planted more than seventeen years, or upon 

 land that grew trees seventeen years ago, the 



