INSECTS 179 



But other visitors still may be noted, and ones which 

 make anything but friendly calls. They, too, come for 

 food, the soft juicy body of the plump little aphid. 

 Among the most interesting and fatal of these carnivorous 

 visitors are the aphis-lions, the fierce larvje of the beau- 

 tiful golden-eyed, lace-winged fly (fig. 136). These may 

 be recognized by their long, slender, pointed mandibles 

 projecting far in front of the head. These mandibles are 

 each grooved along the inner side. When the sharp tips 

 are thrust into the soft body of an aphid its blood runs 

 along the groove into the mouth of the lion. The eggs 

 of the aphis-lion are laid on the tips of slender stalks, to 

 protect them from wandering predaceous insects, includ- 

 ing other aphis-lions. When the larva has made its full 

 growth it spins a spherical silken cocoon, within which it pu- 

 pates. Finally, there emerges the beautiful slender-bodied 

 adult, the lace-winged fly, with four large, gauzy, green 

 wings, and eyes which shine with a fiery golden color. 



Cicadas, katydids, crickets, and their sound-making 

 organs. — Insects familiarly known because of their shrill 

 summer song are the periodical cicadas, or seventeen-year 

 locusts. The second name is really no exaggeration. 

 Although the adult cicadas live in trees and lay their 

 eggs in small slits cut in the twigs, the young, on hatch- 

 ing, drop to the ground and dig down to the roots of the 

 tree. There they suck the juices from the roots by means 

 of a strong piercing beak until the beginning of the 

 summer of the seventeenth year. They then crawl up to 

 the surface of the ground, and, clinging usually to the tree 

 trunk, moult and transform into the fully winged adult, 

 with its shrill song. This is made by a curious musical 

 apparatus on the under side of the body (fig. 1 37), consist- 

 ing of a tympanic membrane or thin plate which can be set 

 into vibration by a muscle attached to its center. It is 

 practically a musical instrument of the type of the tin pan 



