CHAPTER II. 



LIFE HISTORY AND HABITS. 



INSECTS pass through various changes during their lives, changes of 

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

 many cases very great, being the most striking characteristics of the life 

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

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

 We can give 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 are 

 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 chitinous 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 chinges 

 undergone in the great groups of insects. 



FIG. 18. 



Eggs of a Butterfly; natural 

 size on a leaf, and enlarged, 



