ZOOLOGICAL SOCIETY BULLETIN. 



777 



emerged from the earth over a consider- 

 able portion of the eastern United States. 



With the nearby woods resounding with 

 the continuous hum of countless thousands 

 of Cicadas, a great number of inquiries 

 have come to us relating to the possible damage 1 

 to vegetation that will result from these swarms. 

 Hence a review of the habits of this insect is 

 appropriate at this time. 



The Seventeen-Year Cicada, (Cicada septen- 

 rlecim). receives its name from its prolonged 

 larval stage, which covers a period of seventeen 

 years of subterraneous existence. At the 

 expiration of this time, the larva leaves the 

 ground, crawls up a tree trunk or rough 

 stalk of vegetation, and immediately pre- 

 pares to transform into the imago, or 

 winged stage. As it comes from the 

 ground it looks much like a small crusta- 

 cean, without mandibles. The anterior 

 legs are of powerful development and pro- 

 vided with stout hooks. Gaining a firm 

 purchase with these members it prepares 

 to shed the skin or shell. A median slit ap- 

 pears on the thorax or the back and from this 

 emerges a blackish creature with bright red 

 eyes and translucent wings, moist and limp. 

 Withdrawing the limbs from their old casing, 

 the cicada crawls up the tree trunk to rest, while 

 the wings extend and stiffen. Within a few 

 hours it is prepared for flight, but in its 

 wintred stage the perfect insect is permit- 

 ted a very short respite in the sunshine 

 and open air. Its duration of life is now 

 but a few weeks — from twenty to thirty 

 days at the most. Though a voracious 

 feeder during its subterraneous life, the 

 perfect insect is apparently unable to feed 

 owing to lack of development of the mouth 

 parts. The males are provided with vi- 

 bratory organs attached to the posterior 



rtion of the thorax. With these they 

 make the monotonous hum characteristic 

 of a locust swarm. The sound is in no 

 way connected with the mouth parts, a 

 condition existing among all singing in- 

 sects which impart their calls through various 

 stridulating or vibratory organs. The female 

 of the Seventeen- Year Cicada is of particular 

 significance owing to the possession of a lanceo- 

 late ovipositor. It is with this weapon she de- 

 posits her eggs in the terminal branches of trees. 

 When the eggs hatch, the young drop to the 

 ground and burrow. The incisions made 

 by the ovipositor of the female Cicada re- 

 sult in the death of small branches and the 

 malformation of some of the larger ones. 

 This is the only damage from a locust 

 swarm. In fruit growing areas it is liable 

 to he serious. A forest visited by a swarm 

 of this species of Cicada, assumes the ap- 

 pearance about three months after the in- 

 sects have disappeared, as if a superficial 

 fire had swept through it. tinging the ter- 

 minal branches of the larger trees and altogether 

 killing a part of the very young, scrubby growth. 

 The present insect is in no way related to the 

 true locusts, the considerable number of species 

 of which belong to the order Orthoptera, includ- 

 ing the grasshoppers, which are immediately re- 

 lated to the locusts. The imagoes or perfect 

 forms of the Orthopterous insects are vo- 

 racious and most of them comparatively 

 long-lived. Migratory or true swarming 

 locusts do not occur in eastern North 

 Ameirca. The plains states are, however, 

 menaced by these creatures the voracity of 

 which causes great damage. A swarm of 

 migratory locusts settling over cultivated 

 areas leave a region barren of everything 

 green to mark their ravages. 



It is well to understand that the Seven- 



SEVENTEEN-YEAR CICADA. 

 No. 1, male enlarged. No. 2, male from beneath; the white marks on the abdomen show the singing 



from beneath, showing ovipositor. 



organs. No. 3 female 



