226 ANIMAL LIFE 



and sunshine, to harden and exercise their limbs. At 

 regular periods their inflexible skin has to be removed 

 to allow of growth, and a covering one size larger 

 replaces the old coat. As the rate of growth in insects, 

 as in all animals, is fastest at the beginning of life and 

 slows down later on, the skin has to be frequently 

 changed at first, and at longer periods subsequently. 

 We rarely appreciate with what difficulty and danger 

 the process is accompanied. The outer skin is a con- 

 tinuous envelope, softened only at the joints of the 

 body and limbs. Not onty are all the visible parts 

 encased by this covering, but the lining of the mouth 

 and many internal parts are formed by infoldings of 

 this skin. Hence an insect has to sever this intimate 

 union as well as to slip out of its external casing. It 

 must strip its inside and its outside of their protecting 

 envelopes, and the wrench tests all its strength. 



The first act is a rent in the outer garment between 

 the thorax and head, made by forcibly filling the 

 vesicle in the neck until it breaks. Humped up 

 thus, the struggle goes on till the head and neck, with 

 all their appendages, are free. To pull off a jersey is 

 simple compared with the act of pulling away the 

 eyes, the antenna', the jaws, the legs, the mouth, and 

 stomach from their encasing skin. Any holdfast to 

 which the old skin can be hooked and then pulled off 

 is made use of, and at this time the use of many 

 projections on the body is first discovered. The legs 

 gratefully cling to the tail if thereby they may pull 

 themselves out of their casing ; and so with much 



