ZOOLOGICAL SOCIETY BULLETIN. 



777 



emerged from the earth over .a consider- 

 able portion of tlie eastern United States. 



With the nearby woods resounding with 

 the continuous Innn of countless thousands 

 of Cicadas, a great number of inquiries 

 have come to us relating to the possible damage 

 to vegetation that will result from these swarms. 

 Hence a review of the habits of this insect is 

 appropriate at tliis time. 



The Seventeen-Year Cicada, {Cicada scpU'ii- 

 ilecim), 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 slied the skin or shell. A median slit ap- 

 oears 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 U)) the tree trunk to rest, while 

 the wings extend and stiffen. Within a few 

 hours it is prcjjared for flight, but in its 

 winged 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 

 lierfect 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 



SEVENTEEN 

 No. 1, male enlarged. No. 2, male from beneath; the white 



from beneath, 



|)i)rtioii of the thorax. With these they 

 make the monotonous hum characteristic 



rof a locust swarm. The sound is in no 

 way connected with the mouth parts, a 

 condition existing among all singing in- 

 ' sects which imjiart 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- 

 snlt 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 be 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 liad swept through it, tinging the ter- 

 minal branches of tlie larger trees and altogether 

 killing a part of the very young, scrubby growth. 

 Tlie ])resent insect is in no way related to the 

 true locusts, the considerable number of species 

 of which belong to the order Orthoptera, includ- 

 ing tlie grasshoppers, which are immediately re- 

 l.itcd 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 

 ireas leave a region barren of everything 

 green to mark their ravages. 

 3 It is well to understand that the Seven- 



YEAR CICADA. 



marks on the abdomen show the singing organs. No. 3 female 



showing ovipositor. 



