58O ZOOLOGY. 



531. Insects which undergo a complete metamorphosis 

 are always more or less vermiform when they leave the egg 

 and when they are in a state of larva (Fig. 368). Their body 

 is elongated, almost entirely soft, and divided into moveable 

 rings, of which the regular number is thirteen. Sometimes 

 they are altogether without limbs ; at other times they have 

 a variable number of these organs, but whose conformation 

 in no shape resembles that of the same parts in the adult 

 animal. Almost always they have merely simple eyes, and 

 they are sometimes completely without any. Finally, their 

 mouth is almost always armed with mandibles and jaws, 

 whatever be the conformation which they assume in the end ; 

 and we often see the first of these organs serve for locomotion 

 as well as for the prehension of the food. These larvae vary, 

 moreover, in their form, and are known sometimes under the 

 name of cheville (caterpillars) ; sometimes, but erroneously, 

 under the name of worms. 



Fig. 368. Cheville du PapiJlon Machaon (Larva of 

 the Butterfly Machaon). 



After having remained in this condition during a longer or 

 shorter period, and after having experienced several mountings, 

 their wings form under the skin, and they change into nymphs 

 (ckrysalids). During the whole duration of this second 

 period of their existence, these singular animals cease to take 

 food, and remain immovable. Sometimes the skin which 

 they have just shed dries up, and forms a sort of oviform ease, 

 in the interior of which they remain enclosed ; sometimes they 

 are only covered with a thin pellicle, which, applied closely 

 over their external organs, follows all their contours, and 

 resembles linen, in which the insect is encased or bandaged. 

 This last arrangement, which is seen in the nymphs of butter- 

 flies or chrysalids (Fig. 369), has obtained for them the 

 name of pupa or of maillot * 



PM-t'ore undergoing this metamorphosis, the larva often pre- 

 pares a refuge, and shuts itself up in a ease, which it makes 



* Literally, swaddling-clothes. 



