II] 



GROWTH AND CHANGE 



13 



characteristic instar 1 . The first instar differs, how- 

 ever, from the adult in one conspicuous and note- 

 worthy feature, it possesses no trace of wings. But 

 after the first or the second moult, definite wing- 

 rudiments are visible in the form of outgrowths on 

 the corners of the second and third thoracic seg- 

 ments. In each succeeding instar these rudiments 

 become more prominent, and in the fourth or the 



Fig. 5. Nymph of Locust (Schistocera americana) with distinct 

 wing-rudiments. After Howard, Insect Life, vol. vn. 



fifth stage, they show a branching arrangement of 

 air-tubes, prefiguring the nervures of the adult's 



1 The convenient term 'instar' has been proposed by Fischer 

 and advocated by Sharp (1895) for the form assumed by an insect 

 during a stage of its life-story. Thus the creature as hatched from 

 the egg is the first instar, after the first moult it has become the 

 second instar, and so on, the number of moults being always one less 

 than the number of iiistars. 



