ISTRODUCTION. 5 



eacli stage of growth, by the simple process of casting or 

 throwing off a skin. The old skin screens and protects each 

 development until it is complete, and is then flung aside as 

 of no further value. 



The first stage is that of the egg or ovum (plural, ova), 

 which is laid in some suitable place by the parent perfect 

 insect, and out of which, after a period varying from a few 

 days to a few months, creeps the minute caterpillar or larva. 

 This promptly begins to feed, sometimes making its first 

 meal on the horny shell of the ^go,. As it increases in size, 

 its skin becomes too small and is thrown off. This happens 

 in most species three or four times at least, and in some con- 

 siderably more ; but it does not appear that there is a fixed 

 rule in this respect even in the same species. When, how- 

 ever, the larva has fed with increasing voracity until it has 

 attained the full growth applicable to its kind — which may 

 be in twenty-one days or even less, and may be any other 

 length of time up to three or even four years according to its 

 species, and to the time of year — its appetite fails, and it 

 begins to make preparations for a more important metamor- 

 phosis. These preparations are extremely various : some 

 larva3 hang themselves up by the tail, others by that and a 

 silken girth ; others spin around themselves a cocoon or 

 chamber of silk ; others, again, make a chamber of silk and 

 earth, or of earth only ; while many bore into soft wood or 

 bark, or draw together portions of leaves, or creep under 

 moss, or spin up the entrance of the case in which they have 

 lived. All place themselves in some situation which seems to 

 afford protection and safety, and there, after a rest and 

 gradual change — in most species of a very few days, but in 

 some of weeks or even months — another skin is thrown off, 

 and a helpless creature is disclosed, having neither means of 

 feeding nor of locomotion, nor indeed of any motion, except 

 of the rings or segment of the abdomen by which the old skin 

 is shaken or thrust off. This helpless body is called the 

 chri/sulis or jv'jta. In this condition it remains fur a few days 



