INSECTS 



caterpillar, for example, certainly is not a form headed 

 toward a butterfly in its growth, and yet we know it is a 

 young butterfly because it hatches out of the butterfly's 

 egg. And, as the caterpillar grows from a small cater- 

 pillar to a large caterpillar, it becomes no more like a 

 butterfly than it was at first. It is only after it has 

 reached maturity as a caterpillar that it undergoes a 

 process of transformation by which it attains at last the 

 form of the insect that produced it. 



The question now arises as to whether the butterfly is a 

 form superadded to the caterpillar, or the caterpillar a 

 form that has deviated from the developmental line of 

 its ancestors. This question is easily answered: the but- 

 terfly represents the true adult form of its species, for it 

 has the essential structure of all other insects, and it alone 

 matures the sexual organs and acquires the power of re- 

 production. The caterpillar is an aberrant form that 

 somehow has been interpolated between the egg and the 

 adult of its kind . The real metamorphosis in the life of 

 the butterfly, therefore, is not the change of the cater- 

 pillar into the adult, but the change of the butterfly 

 embryo in the egg into a caterpillar. Yet the term is 

 usually applied to the reverse process by which the 

 caterpillar is turned back into the normal form of its 

 species. 



The caterpillar and the butterfly (Fig. 128) furnish the 

 classical example of insect metamorphosis. Many other 

 insects, however, undergo the same kind of transforma- 

 tion. All the moths as well as the butterflies are cater- 

 pillars when they are young: the famous giant moths 

 (Plate 10), including the Cecropia, the Promethea, and the 

 beautiful Luna (Fig. 129), as every nature student knows, 

 come from huge fat caterpillars; the humble cutworms 

 (Fig. 130), when their work of destruction is completed, 

 change into those familiar brown or gray furry moths of 

 moderate size (A) often found hidden away in the day- 

 time and attracted to lights at night. In the spring, the 



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