THE PERIODICAL CICADA 



Fig. i 14. Nymph of the periodical 

 cicada in the fourth stage, about 12 years 

 old, enlarged 1}i times. (From Marlatt) 



stage, which is about a year in length. In the fourth 

 stage, which lasts perhaps three or four years, the nymph 

 (Fig. 114) shows distinct wing pads on the two wing- 

 bearing segments of the 

 thorax. In the fifth stage 

 the insect, sometimes now 

 called a "pupa," takes on 

 the form it has when it 

 finally emerges from the 

 earth; its front feet are 

 restored and its wing 

 pads are well developed, 

 but it has entirely lost its 

 small nymphal eyes. 

 Once more, before its 

 long underground sen- 

 tence is up, the nymph molts, and enters the sixth and 

 last stage of its subterranean life. When mature (Plate 5) 

 it is about an inch and a quarter in length, thick-bodied, 

 and brown in color; it appears to have a pair of bright-red 

 eyes on the head, but these are the eyes of the adult 

 inside showing through the nymphal skin. 



According to the investigations of Doctor Marlatt, the 

 nymphs of the periodical cicada do not ordinarily burrow 

 into the earth below two feet, and most of them are to be 

 found at depths varying from eight to eighteen inches. 

 However, there are reports of their having been discovered 

 ten feet beneath the surface, and they have been known 

 to emerge from the floors of cellars at the time of trans- 

 formation to the adult stage. There is no evidence that 

 the insects, even when present in great numbers in the 

 earth, do any appreciable damage to the vegetation on 

 the roots of which they feed. 



Some time before the mature nymphs emerge from the 

 ground, probably in April of the last year of their lives, 

 the insects come up from their subterranean burrows and 

 construct a chamber of varying depth just below the 



[187] 



