CHAPTER II. 



LIFE HISTORY AND HABITS. 



INSECTS pass thvoug-h various chaiig-os diirino- thoir lives, ehan^^es of 

 form, habits, structure and the like ; these transformations are in 

 many cases very g-reat, being- the most striking- characteristics of the life 

 history of insects. Whilst the life history is essentially the same through- 

 out larg-e groups of insects, it is not exactly the same in any two species. 

 We can g-ive here only a very brief outline, but fuller details will be found 

 in the later sections. 



Insects are hatched from eggs, which, though smaller and different 

 in appearance, are essentially similar to those of birds. These eggs arc 

 not cared for by the parent insect, but are laid in such a position that the 

 young when they emerge will find suitable food. 



From the eggs hatch out tiny insects which are usually able to feed 

 almost at once and begin their active life without delay. They feed 

 voraciously and rapidly grow larger. Their cliitinous skin will, however, 

 not stretch and permits of growth only to a certain limit ; when this is 

 reached, a new soft skin is formed under the old one ; the latter splits 

 so that the insect crawls out with only the new soft skin ; the insect at 

 once expands, the new skin hardens with the result that our little insect 

 is suddenly twice its previous size and perhaps 



very different in appearance. Growth again 



continues until the insect is too large for the 



second skin, when the process is repeated and 



a fresh moult undergone. The skin is thus 



shed periodically until the insect attains its 



full size and mature form. At every moult 



the appearance of the insect changes ; it may 



be a minute change in appearance with a 



considerable change in size, or it may be a com- 

 plete change of form, with change of habits 



and structure. The number of moults varies 



from two to twenty or more, but is generally 



about five to seven. 



These changes form the essential part of 



the life history of insects. We can now 



examine in detail the nature of the changes ^^*^' ^^' 



J • ii J c • , £lo(JS of a Butterfly; natural 



undergone m the great groups of msects. Ze on a leaf, and enlarged. 



