208 



BIOLOGY FOR BEGINNERS 



This pupa stage in which the lepidoptera usually pass the winter, 

 is not really a period of entire rest. Marvelous changes take place 



which are not well understood, 

 but this at least is known, the 

 worm-like larva emerges totally 

 changed both in internal and 

 external structure, as the adult 

 butterfly or moth. 



Whereas the larva's func- 

 tion was to eat and grow, the 

 adult eats only the nectar of 

 the flowers and its life work 

 is to produce or fertilize the 

 eggs for the next generation. 



Such a life development, 

 consisting of distinct stages, 

 is called complete metamor- 

 phosis, as distinguished from a 

 life history of gradual changes 

 (like the grasshopper) which is 

 called incomplete metamor- 

 phosis. Complete metamor- 

 phosis is not confined to the 



FIG. 67. Diagram of wings of 

 monarch butterfly, Anosia plexippus, 

 showing venation, c, costal vein; s.c., 

 subcostal vein; r, radial vein; ca, cubital 

 vein; a, anal veins. In addition, most 

 insects have a vein lying between the 

 subcostal and radial veins, called the 

 medial vein. Natural size. From 

 Kellogg. 



lepidoptera. The bees, beetles, 

 and flies all pass through 

 similar series of changes 

 which can be tabulated as 

 follows: 



f Deposited near source of food 



I Period of increase in number 



f Period of eating and growth (usually harmful) 



I Worm, grub, or maggot stage 



f Period of quiet, internal transformation 



\ Usually pass winter in this stage 



( Cocoon or chrysalis 

 Adult Reproductive stage 



Egg 



Pupa 



