DEVELOPMENT AND METAMORPHOSIS. 39 



roundings that it might be visible but not distinguishable. 

 The insect in its pupal stage does not eat, but the larva 

 has provided for this by eating greedily all through its 

 larval existence ; so there is a large supply of surplus food 

 within the larval body when the pupa begins the wonder- 

 ful changes toward adult form. Upon this reserve the 

 pupa draws until the time of its emergence as an adult. 

 Although the pupal insect does not eat, nor, except in 

 a very few cases, move about from place to place, we are 

 not to regard it as quietly doing nothing while it is in its 

 burrow or cocoon. Really this is the period of the most 

 wonderful changes in all the insect's life. Gradually 

 there comes about, in the case of the tomato worm, for 

 instance, the replacement of the solid food digesting 

 apparatus, with the alimentary organs necessary for 

 digesting liquid food; the caterpillar set of muscles must 

 be replaced by the wing and the leg locomotor muscles; 

 the wings themselves must be developed; the wonderful 

 compound eyes must be built, facet by facet, with the 

 marvelous structure behind each. Embryologists tell 

 us that this building up of new organs is preceded by a 

 breaking up of most of the internal organs into a general 

 body fluid, out of which rich food supply, the new organs, 

 internal and external, must be built, with perhaps 

 certain bud cells as centers for the new growths. 



All young animals, even the one-celled, have a 

 longer or shorter period of immaturity. In the cases 

 where the young of insects are born alive we must conceive 

 these changes as having taken place before the young 

 were freed from the egg duct of the mother insect, as is 

 the case with such of our flies as do not "lay eggs." In 

 complete metamorphosis the insect is born youngest, 

 is most immature, and appears in the form farthest 



