CICADAS, PLANT LICE, AND SCALE INSECTS 31 



The female of the periodical cicada lays her 

 eggs in slits, usually in the small terminal twigs 

 of trees. In a year in which these insects ap- 

 pear in large numbers the trees look as if a fire 

 had passed over them and scorched the ends 

 of all the twigs. The eggs hatch in about six 

 weeks, and the nymphs drop to the ground, 

 into which they dig. For a long period of time,' 

 thirteen years in the Southern states and seven- 

 teen years in the North, they lie in a cell, 

 feeding on the juices of the roots of trees. 

 Early in the summer of the thirteenth or 

 seventeenth year, they rise to the sur- 

 face, and, clinging to some convenient 



support (Fig. 16, A), 

 cast their last nymph 

 skin (Fig. 16, B) to 

 come out as winged 



Fig. 15. A study of the periodical cicada, (x J) 



Female depositing eggs in stem of a plant, nymphal skin from which an 



adult has emerged, and chimneys 



