47 



PART II. 



ON THE WINGED INSECTS. 



CHAP. I. 



ON THE PTILOTA, OR FOUR-WINGED INSECTS IN GENERAL, THE 

 CHARACTERS OF THE FIVE ORDERS, AND THEIR MUTUAL RE- 

 LATIONS TO OTHER ANIMALS. THE METAMORPHOSES OF IN- 

 SECTS. 



(42.) All insects, without any exception, possessing 

 four wings, enter into one or other of the orders com- 

 posing the Ptilota, a class first instituted by Aristotle, 

 and adopted by us, as the first and foremost of the an- 

 nulose animals. We have already shown, that as the 

 possession of wings is the primary distinction of one of 

 the great divisions of the vertebrate animals, so the 

 highest development of these members among the 

 Ptilota points them out as the pre-eminent types of 

 the Annitlosa. This is their primary distinction ; and 

 it pervades nearly every genus. Sometimes, indeed, 

 we meet with a few examples of apterous insects ; but 

 these are only instances of those exceptions which occur 

 in every natural group, and are hardly worth mention- 

 ing in a general definition. The Ptilota possess some 

 other characters, not indeed altogether peculiar to them- 

 selves, but yet more striking and universal among them 

 than in the apterous orders. They exhibit, collectively, 

 the most perfect instances of metamorphosis ; their legs 

 are never more than six, and the head is always distinct 

 from the body. Were we to descend to other definitions 

 of the class, we should be so encumbered with excep- 

 tions, that the student would be perplexed, and the 



