Bugs, Cicadas, Aphids, and Scale-insects 167 



life of but one or two years. But few species of cicadas, dog-day locusts, 

 harvest-flies, or lyremen, as they are variously called, occur in this country 

 they are more abundant in subtropic and tropic countries but their 

 large, robust, blunt-headed body, their shrill singing and their wide dis- 

 tribution make them familiar insects. 

 In summer and fall the piercing, 

 rhythmic buzzing of the cicadas comes 

 from the trees from early morning 

 till twilight. The song, unlike that 

 of the katydids and tree-crickets, is 

 hushed at night. The sound is made, 

 not by a rasping together of wings 

 or legs, but by stretching and relaxing 

 a pair of corrugated tympana, or 

 parchment-like membranes, by means 

 of a muscle attached to the center 

 of each; much, indeed, as a small 



boy makes music from the bottom of FIG. 235. The seventeen-year cicada, 



. Al . . , j , Cicada septendecim; specimen at left 



a tin pan with a string fastened to its showing ound _ makin organ . v . p . t 



center. These sound-making organs ventral plate; /., tympanum. (Natural 

 of the cicadas, confined to the males 



"Happy is the cicada, since its wife has no voice," says Xenarchos are 

 situated in resonance-cavities or open boxes, furnished with other sym- 

 pathetically vibrating membranes, at the base of the abdomen (Figs. 235 

 and 236). The sound-chambers are closed internally by the vibrating 



membranes and covered over externally by a 

 pair of semicircular disks, which are opened or 

 shut by movements of the body so as to give 

 the song a peculiar rhythmic increase and de- 

 crease of loudness. 



The cicada that is most familiar, and on hand 

 every summer over most of the country, is the 

 large (2 inches in length to tip of closed wings) 

 black and green dog-day harvest-fly, Cicada 

 Fin. 236. Diagram of section tibicen. The life-history of this species is not 

 of body of cicada, showing full known but the insect requires, accord- 

 attachment of muscles to inner 



surface of sound-making ing to Comstock, two years to become mature, 

 organ. (Enlarged.) xhe really famous cicada is Cicada septen- 



decim, the seventeen-year locust, or periodical cicada (Fig. 235). It is 

 about ij inches long, black, banded with red on the abdomen, and with 

 bright red eyes and the veins of both wings red at the base and along the 

 front margin. The females lay their eggs in early summer in slits which 



