22 Descriptive Zoology. 



sound made by the males. Under the abdomen of the 

 males are two circular disks. Under these is the appa- 

 ratus by which the sound is produced. 



Both pairs of wings are membranous, the hinder pair 

 being much the smaller. The larva is a grublike form 

 which lives under the ground, sucking the juices from the 

 roots of trees. When ready to appear in the upper world, 

 it crawls up the trunk ; and while it still clings to the bark 

 its back splits open, and the winged insect emerges, leaving 



FIG. ii. CICADA: HARVEST FLY. 



From Hyatt's Insect a. 



the empty skin adhering by the claws. Here the shed skin 

 may remain for weeks, until washed off by the rain or 

 brushed off by a passing animal. 



The dogday harvest fly (Fig. 1 1) has a very broad head 

 with eyes projecting at its angles, and is rather greenish. 

 His shrill sound is suggestive of the dry, hot, August mid- 

 day. The periodical cicada (the correct name for what is 

 usually called the " seventeen-year locust") spends from 

 thirteen years in the Southern form to seventeen in the 

 Northern in the larval state. This cicada is distinctly nar- 

 rower-headed than the summer cicada, and is darker in 

 color. 



