BUTTERFLIES AND MOTHS 3041 



other woolen stuffs, gnawing ragged holes, and when the imago or perfect insect 

 appears the mischief has been done. So voracious are larvae that huge oak forests 

 may be in a few days swept bare of almost every vestige of foliage. 



The body consists of a head bearing biting mandibles for nipping off 

 the edges of leaves, or gnawing among decaying timber; a pair of small, 

 short antennas form appendages on either side; and just behind three 

 simple eyes, or ocelli, on either side, very different from the large compound eyes 

 of the perfect insect. Behind the head lie eleven segments or movable rings. 

 Three of these, close behind the head, correspond to the thorax of the adult, and 

 bear the three pairs of thoracic legs, short and horny, exactly corresponding to the 

 three pair of legs of the butterfly or moth. The other segments bear the prolegs or 

 claspers varying in number from one to five pairs used for clinging to leaves 

 and other surfaces. In some of the moths the last pair are obsolete as legs, and are 

 developed into a pair of horns, supposed to be for protective purposes, as, for 

 instance, in the puss moth. A caterpillar may thus possess sixteen legs, though 

 often there is not the full number. 



A very curious form of larva is that producing the insects known as the 

 geometers, so called because of the peculiar gait of the caterpillar, which measures 

 out the surface over which it passes with a regular series of equal strides or loops. 

 Their body is long, but since there are but four prolegs, they cannot crawl, but by 

 bringing up the hinder-legs, advancing the head, and again bringing forward the 

 tail, the caterpillar spans the space to be traversed by a series of looping strides. 

 Hence the Americans call them " span worms." These larvae, too, are remarkable 

 for their resemblance when the head is stretched outward to a broken twig, a 

 likeness which undoubtedly secures them from many dangerous foes. Many larvas 

 are protected by their similarity in color to the surrounding foliage, and it has been 

 supposed that the pigment from the leaves which the caterpillar eats lends its 

 characteristic hue to its devourer. From the moment of hatching until the final 

 molt, when the caterpillar enters the pupa state, it undergoes a series of from eight 

 to ten changes of the skin. These changes form crises in the lives of larvae, which, 

 at any rate in captivity, sometimes die during the process. 



The stage immediately preceding that of the perfect form is usually 

 called, when reference is made to the butterflies, the chrysalis state; 

 but in the case of the moths, the pupa state, though there is no essential difference 

 between the two. In this strange quiescent state the wings, legs, antennae, and 

 proboscis of the future insect can be seen fully formed and folded tightly within the 

 outer covering. The only signs of vitality are given by wriggling movements of 

 the segmented abdomen, when the pupa is irritated. The hard external covering is 

 useful for resisting the attacks of predaceous insects, though of course not securing 

 them immunity from mice, birds, or moles, which devour them with avidity. The 

 chrysalis of a butterfly is usually angular and gilded. Some are suspended simply 

 by the tail, others have a silken girdle round the middle to keep them fast, while 

 some spin a very slight cocoon. The pupae of the moths, on the other hand, are 

 dull red, usually smooth mummy-like objects, to which likeness the word pupa or 

 "puppet" doubtless refers. The greater part of these lie simply in the earth, 

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