<5o TRANSFORMATIONS OF INSECTS. 



extended and shortened, as if the insect were in the act of laborious 

 respiration. This generally takes place at short intervals during 

 the two hours immediately preceding the change, and increases 

 in frequency as that period approaches. When that period has 

 arrived, the skin bursts along the back part of the third segment, 

 or mesothorax, and is extended along the second and fourth, while 

 the coverings of the head separate into three pieces. The insect 

 then exerts itself to the utmost to extend the fissure along the 

 segments of the abdomen, and in the meantime, pressing its body 

 through the opening, gradually withdraws its antenna; and legs, 

 while the skin, by successive contortions of the abdomen, is 

 slipped backwards, and forced towards the extremity of the body, 

 just as a person would slip off his glove or his stocking. The 

 efforts of the insect to get entirely rid of it are then very great ; 

 it twists itself in every direction, in order to burst the skin, and 

 when it has exerted itself in this manner for some time, twirls 

 itself swiftly, first in one direction and then in the opposite, until 

 at last the skin is broken through and falls to the ground, or 

 is forced to some distance. The new pupa then hangs for 

 a few seconds at rest, but its change is not yet completed. The 

 legs and antennae, which when withdrawn from the old skin were 

 disposed along the under-surface of the body, are as yet separate, 

 and do not adhere together as they do a short time afterwards. 

 The wings are also separate, and very small. In a few seconds 

 the pupa makes several slow but powerful respiratory efforts, 

 during which the abdominal segments become more contracted 

 along their under-surface. The wings are then much enlarged and 

 arc extended along the lower surface and sides of the body ; more- 

 over, a very transparent fluid, which facilitated the slipping off 

 of the skin, is now diffused among the limbs, and when the pupa 

 becomes quiet, dries and unites the whole into one compact 

 covering. Exactly the same thing occurs in the changes of the 

 Sphinx. The limbs at first arc all separate, each one being 

 enclosed in its distinct sheath, but within a very short period after 

 the change they become agglutinated together by the fluid diffused 

 between them, and form the solid exterior of the pupa case. 



"The three thoracic legs can be distinguished from the mem- 

 branous legs of the hinder segments. Within the body, and 



