98 



Marvels of Insect Life, 



The wings also exist in the caterpillar in the shape of folded buds. The feeding of the 

 caterpillar results in the storing of a large quantity of formative material known 

 as the fat-body. In the chrysalis this is drawn upon to provide for the growth of 

 the wings and other structures of the complete Insect. The chrysalis is formed, 

 of course, before the last caterpillar skin is cast off. A little before what is generally 

 known as pupation, the full-grown caterpillar ceases to eat, and the pupal structures 

 then undergo rapid expansion at the expense of the fat-body. Changes take place in 

 the nervous system and the digestive system, and at the same time the purely larval 

 structures are breaking down and being formed into parts of the new structures. 

 The caterpillar skin splits in the fore-part of the back and the chrysalis draws 

 itself out of the opening, and by systematic wriggling pushes the old skin back 

 over the narrow hind extremity. This is furnished with hooks which it now 



catches in the little pad of 

 silk previously spun by the 

 caterpillar for the purpose. 

 At this time the legs, 

 antennae, and wings are all 

 loosely folded on the ex- 

 terior of the chrysalis, but 

 a transparent fluid is now 

 poured out which covers 

 the entire creature, and 

 rapidly hardening into a 

 film, glues down all the 

 parts. It is this film which 

 is split at a later stage 

 to release the completely 

 developed butterfly. We 

 say completely developed 

 because, although the 

 wings are small and 

 crumpled on emergence, 

 they are fully formed and 

 need only distension by 

 the inflation of the air-tubes and the circulation of blood between the two membranes 

 of which the wing consists. 



In the foregoing we have taken the butterfly as an example of those Insects 

 in which the metamorphosis is complete. In the others it will be understood that 

 the adult form, minus wings, having been reached when the Insect leaves the egg, 

 the internal changes are not of a revolutionary character, and are mainly concerned 

 with the development of the reproductive system. In the butterfly, the beetle, 

 the bee, and the fly, the perfect Insect being so different from the larva, the latter 

 contains imaginal discs or buds for every part of the future body. In most cases 

 the whole of this important series of changes is passed through very rapidly. To 

 give an example that will show at once the rapidit}^ of change and the vast increase 



Photo by] 



A Caterpillar. 



In this photograph of the privet hawk-moth caterpillar several points described in the 

 letterpress are clearly shown. Just behind the head are the three pairs of permanent legs 

 which develop into the six legs of the moth ; below the middle of the body are the four 

 pairs of temporary unjointed legs, and at the hinder extremity the pair of powerful 

 claspers, which are also temporary. 



