i68 THE BIOLOGY OF INSECTS 



heads with large eyes and short feelers ; the front legs are 

 stouter than those of the middle and hind pairs. They have 

 ample wings and fly about in the woodland regions alighting 

 on trees from whose leaves they suck sap. The habits and 

 life-history of the common North American Tibicina septen- 

 decim (Fig. 44) have been well described by C. L. Marlatt 

 (1907) and R. E. Snodgrass (1921). The female cicad 

 possesses a long cutting ovipositor wherewith she excavates 

 slit-like cavities or " nests " in the twigs of trees and 

 deposits her eggs therein. The young, when hatched, live 

 for a time crawling about the branches of their native tree 

 and then drop to the ground and burrow into the soil. 

 The newly hatched cicad-larva (Fig. 44, a) differs from its 

 parent by its soft, pale cuticle, its elongate ovoid head with 

 relatively long feelers and small eyes, its regularly segmented 

 body with little differentiation in the various regions, and 

 its very broad and powerful fore- legs with the spinose tip 

 of the sliin adapted for burrowing. The successive stages 

 of the life-history are passed underground, and during 

 these the foot (tarsus) of the fore-limb, well developed in 

 the newly hatched young, becomes greatly reduced. In the 

 two well-marked races of Tihicina septendecim it is well 

 known that the growth and transformation of the individual 

 insect is carried on through a period of twelve and sixteen 

 years respectively." Such excessively lengthened life-cycles 

 afford extreme instances of a condition often to be noticed 

 in insect development — a prolonged period of preparation 

 through most of which the creature feeds and grows, leading 

 up to a comparatively brief adult existence the beginning 

 of which usually marks the end of growth and change, and 

 which, whether the creature's way of life and manner of 

 feeding are like or unlike those of its early stages, is 

 strikingly curtailed in its relation to the prolonged period 

 of immaturity. 



In their manner of development cicads display yet 

 another feature of much general interest. After the long 

 underground life of years during which the creature feeds 

 by sucking sap from roots which it pierces with its needle- 



