12 ANIMAL BIOLOGY 



from time to time sheds or molts the more or less hardened 

 skin that covers the whole insect. At last, after several 

 molts, the caterpillar reaches its full size and then stops 

 eating. At no time in the growth of the caterpillar would 

 one be likely to mistake it for a butterfly (Fig. 6). It has 

 no wings, no antennae, and instead of a proboscis one finds 

 a pair of strong jaws with which it eats leaves. The distinc- 

 tion between thorax and abdomen is not at all clear, and at 

 first sight it seems to have more legs than a butterfly. The 

 three front legs are really jointed, but they are so short and 

 thick that there seems to be no resemblance between them 

 and those of a butterfly. The other pairs of legs, varying 

 injiumber, are not jointed structures, and hence are not really 

 legs at all. 



The mature caterpillar now attaches itself to some object 

 and, after molting once more, usually assumes quite a different 

 shape from that of the caterpillar, and forms about itself 

 a hardened skin within which a marvellous transforma- 

 tion occurs (Fig. 6). The long, coiled tube takes the place 

 of the jaws as a feeding organ, and long, slender, knobbed 

 antennae appear on the head; two pairs of beautifully 

 colored wings develop on the thorax, as well as the three 

 pairs of slender, jointed legs ; and at last the fully developed 

 butterfly breaks through the covering that held it and flies 

 away. 



It is evident, then, that a butterfly passes through several 

 fairly distinct stages. First we may distinguish the egg 

 stage, then the caterpillar or larva stage, which is followed by 

 the transformation stage in which it is called a pupa. The 

 pupa of a butterfly is often called a chrysalis (Greek, chrysos 

 = gold) on account of the golden spots of color on many 

 pupa cases. Lastly we have the fully developed or adult 

 insect that emerges from the pupa stage. 



