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 



FK;. ii. CICADA: HARVEST FLY. 



From Hyatt's Insecta. 



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. 



