114 METAMORPHOSES, INSTINCTS, AND CLASSIFICATION. 



twelve days, they shut themselves up in a small silky shell, of 

 extreme delicacy, and are there transformed into a chrysalis ; at 

 the end of about twelve days of seclusion, if the weather is warm, 

 they come out of their envelope in a perfect state. 



634. Again, there are some Insects which do not pass 

 through any metamorphosis, and which are born with all the 

 organs with which they will ever be provided ; but it is only 

 among Apterous^ or wingless, Insects, that this mode of deve- 

 lopment exists. The Podura, which has been already referred 

 to, and the Louse, are of this kind. 



635. The class of Insects, which (as we have seen) is so 

 remarkable for its organisation, is still more so in regard to the 

 habits of the animals composing it, and the admirable instincts 

 with which Nature has endowed a great number of them. The 

 stratagems which they employ to procure themselves food, or to 

 escape from their enemies, and the industry which they display 

 in their labours, astonish all those who are witnesses of it ; and 

 when we see them unite themselves into numerous societies, to 

 make up for their individual weakness, helping each other by 

 dividing the labour necessary for the prosperity of the commu- 

 nity, providing for their future wants, and often even regulating 

 their actions according to the accidental circumstances in which 

 they find themselves placed, we are confounded at encountering 

 amongst beings so small, and in appearance so imperfect, instincts 

 so varied and so powerful, and intellectual combinations which 

 so much resemble those of the reasoning powers. This subject 

 will be more fully treated of in the latter part of the present 

 volume. At present we must confine ourselves to a sketch of 

 the classification of this group ; which, on account of the immense 

 number of forms included in it, must be more slight than that 

 which has been given of the preceding classes. 



636. The subdivision of the Class into Orders is founded 

 chiefly upon the structure of the Mouth, the conformation of the 

 Wings, and the nature of the Metamorphosis. Neither of these 

 characters must be trusted to singly ; since within the limits of 

 one group, we find considerable variation. Thus in almost every 

 order, we meet with apterous or wingless insects ; an example of 



