FORM, GROWTH, AND CHANGE 37 



rudiments are larger, the costa of the forewing equalling, in 

 some cases, the prothorax in length. This stage is the last 

 but one, being followed by the final, fully-winged imago 

 (Fig. ig/) or perfect insect. 



Although the grasshopper's development after hatching 

 pursues a regular and even course, unmarked by any striking 

 change, the assumption of the final, winged condition is a 

 noteworthy episode. The last moult is brought about in the 

 same manner as the preceding ones ; the old cuticle splits 

 dorsally lengthwise, and the head and thorax of the new 

 instar are disengaged first, then the front and the middle legs 

 and the wings, then the abdomen and hindlegs, the latter 



a 



FIG. 2O. THREE STAGES ((I, b, C) IN THE EMERGENCE OF THE ADULT ROCKY MOUNTAIN LOCUST 



(Caloptenus) FROM THE LAST NYMPH-CUTICLE. 



In c, the insect has reversed its position and the wings are drying. Natural size. After Riley, 

 Entom. Bull. 25, U.S. Dept. Agric. 



being sharply flexed at the knee-joint, so that the shin lies 

 close against the thigh. Before this moult, the insect has 

 climbed to a shoot of some convenient plant to which it clings 

 by its feet, and the winged instar emerges so that it hangs 

 almost vertically head downwards (Fig. 20 a), only the hinder 

 region of the abdomen remaining within the old cuticle ; in 

 this position, the abdomen becomes distended through the 

 absorption of air, and attains its full length. Before the 

 withdrawal of the tail region from the old cuticle, the abdomen 

 is strongly bent, so that the feet of the front and middle legs 

 can grasp the plant-shoot up which the former instar had 

 previously crawled. Then the emergence is completed, and 



