24 



ZOOLOGY 



their larval skin (Fig. 21), and fly away as full-grown cicadas. 

 In the case of our more familiar species of cicada there is a brood 

 e^'ery year. 



Besides the cicadas the Homoptera include the little leaf- 

 hoppers and tree-hoppers, the very destructive scale-bugs 



(Fig. 22), the mealy bugs, most of 

 •\\-hich attack fruit trees and their 

 fruits, and the plant-lice, or aphids 

 (Fig. 2.3). 



The follomng groups, containing 

 relatively few important species, 

 are placed in this chapter with the 

 Orthoptera although they are not 

 closelj' related to that order. 



The may flies (Ephemeridse) 

 are large winged insects which are 

 seen in great numbers in early 

 summer. Their fore wings are 

 fineh' veined and much larger than 

 the hind wings. The mouth parts 

 are rudimentary, and there are two 

 or tliree thrcadhke appendages at 

 the tail end of the liody (Fig. 24). 

 As the systematic name implies, they have a very ephemeral 

 exist;mce in the winged or imago state. The imagos appear 

 in swarms, eat nothing, and live onlj' a few hours, to deposit 

 their eggs upon or under stagnant water. The larvae hatch 

 in the water, feed upon small aquatic plants and insects, 

 breathe by means of gills borne upon the back, and live in this 

 immature condition for one, two, or even three years (Fig. 25). 

 After many molts the mnged form emerges from the water 



Fig. -1. — Pur»alf;ise cf ciradu. 

 Two-thirds iiat. size. Photo, 

 by W. H. C. P. 



