20 CLASS INSrCTA. 



is then viviparous. The number of annual generations of 

 a species, depends on the duration of each of them ; most 

 frequently there is but one or two in the year. A species, 

 cceteris paribus.^ is so much the more common, as the gene- 

 rations succeed each other with more rapidity, and the 

 female is more fruitful. 



A female butterfly, after copulation, lays her eggs, from 

 which spring, not butterflies, but animals with a very elon- 

 gated body, divided into rings, with a head provided with 

 jaws, and several small eyes, having very short feet, six of 

 which are scaly and pointed, placed in front, the others 

 variable in number, membranous and attached to the final 

 rings. These animals, known under the name of caterpil- 

 lars, live for a certain time in this state, and change their 

 skin many times. Finally, there arrives a period when from 

 this skin of the caterpillar issues a being totally diff*erent, of 

 an oblong form, without distinct limbs, and which soon ceases 

 to move, remaining a long time apparently dead and dried 

 up, under the denomination of chrysalis. When we ex- 

 amine it pretty closely, we discover, in relief^ on the external 

 surface of this chrysalis, certain lineaments which represent 

 all the parts of the butterfly, but in proportions different 

 from those which these parts will one day possess. After a 

 period more or less long, the skin of the chrysalis opens, and 

 the butterfly comes forth, humid, soft, with short and flaccid 

 wings. But in a few moments it dries, its wings grow, be- 

 come strong, and it is in a state to fly. It has six long feet, 

 antennae, a spiral proboscis, and complicated eyes ; in a word, 

 it resembles in nothing the caterpillar from which it has 

 sprung, for it has been verified that the changes of state are 

 nothing else but successive developments of the parts con- 

 tained one in the other. 



All this is what is termed the metamorphoses of insects. 



