CLASS INSECTS. 425 



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 larvse vary, 

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

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

 under the name of worms. 



Fig. 447. Chrysalis of the Machaon ; Swallow-tailed Butterfly. 



After having remained in this condition during a longer or 

 shorter period, and after having experienced several moultinqt, 

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

 (cliry solids]. 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 case, 

 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 chry solids (Fig. 447), has obtained for them the 

 name of pupa or of maillot* 



Before undergoing this metamorphosis, the larva often pre- 

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

 with silk, secreted by glands analogous to the salivary glands, 

 and prepared by means of winders -hollowed out in its lips. 

 At other times it suspends itself by means of filaments (Fig. 

 447), or conceals itself in some hole. It is while the insect 

 is in this state of apparent repose that there takes place in 



* Literally, swaddling-clothes. 



