76 



The Rocky Mountain Locust. 



They all escape, one after the other, through one small 

 hole, which in the field is scarcely noticeable. Such is the 

 usual mode of hatching ; but when the young from the 

 lower eggs hatch first, or when the upper eggs perish and 

 leave the lower ones sound — as is not unfrequently the 

 case — the exit is nevertheless easily made along the chan- 

 nel already described (Fig. 9, c). 



Where there is the heat requisite to insure development, 

 but insufficient moisture to weaken the egg-shell, it is not 

 improbable that another agency comes into play to aid the 

 escape of the young. 



Every one who has been troubled by it must have 

 noticed that the shanks {tibice) of our locust, as of all the 

 members of its family, are armed with spines. On the four 

 anterior legs, these spines are inside the shank ; on the 

 long posterior legs, outside. The spines of the hind 

 shanks are strongest, and the terminal ones on all legs 

 stronger than the rest. There can be no doubt that these 

 spines serve to give a firm hold to the insect in walking 

 or jumping ; but they may have first served a more im- 

 portant prenatal purpose by partially performing the office 

 of egg-burster. 



When fully formed, the embryon is seen to lie within its 

 shell, as at Fig. 10, c. The antennae curve over the face 

 and between the jaws, which are early developed, and 

 which, with their sharp, black teeth, reach down to the 

 breast. The legs are folded up on the breast, the strong 

 terminal hooks on the hind shanks reaching toward the 

 mesosternum, or middle-breast. Ordinarily all these parts 

 are sheathed m the delicate pellicle (amnion) presently to 

 be described. But just in proportion as the hatching is 

 retarded for want of moisture, after the embryon is once 

 fully developed, in that proportion the jaws and spines 

 harden ; and it would seem that by the muscular contrac- 



