48 -^N ECONOMIC ENTOMOLOGY. 



veloped will be like the parent that laid it, and never anything 

 else. Insects are as a rule unable to reproduce until they have 

 reached the adult stage, and the few apparent exceptions may 

 not be real when all the factors are understood. An insect, when 

 once adult, never changes into one of a different kind ; so a 

 beetle can never change into a cricket, nor a small fly into a 

 larger one. 



CHAPTER VIII. 



GROWTH AND METAMORPHOSIS. 



Insects grow only in the larval stage, and moult, or change 

 their skin, every time there is an increase in size. As has been 

 stated, the insect crust is rigid and inelastic, and extension is 

 possible only by the expansion of the membrane between the 

 rings. When a growing insect reaches the extent of the elasticity 

 in its covering, a new skin forms beneath the old one, and the 

 latter splits, allowing the newly-clad and much larger specimen 

 to crawl out of it. In this respect insects resemble crabs, lobsters, 

 and other crustaceans. 



The terms larva, pupa, and adult have been several times used 

 in the previous chapters, and need more explanation. Most 

 insects undergo, in the course of their life, a series of changes or 

 transformations, in which their form, appearance, and habits are 

 often so diverse that the different stages could not be recognized 

 as belonging to one species without definite, continued observa- 

 tion. These changes are termed metamorphoses, and they 

 include the egg, larval, pupal, and adtilt stages. With few 

 apparent exceptions, all insects begin in an e^^ stage, and the 

 method in which this ^^^ is developed has been already described. 

 In this stage, whether it be long or short, the creature is unde- 

 veloped and quiescent, except for the changes going on within, 

 and which do not result in outward movement. In rare cases 

 the eggs are not extruded from the body of the insect, but fertili- 

 zation takes place in the ovary, the larvae hatching within the 

 abdomen of the mother. 



From this ^^^ comes in due time a larva, a minute creature 



