CHAPTER XIV. 



THE ANOPLURA — THE THYSANURA. 



These are the most degraded forms of insects, and they never 

 obtain, during any time of their lives, those elaborate structures 

 which are usually considered to be characteristic of the class. 

 The members of the species of Anopliira and Thysamira are 

 invariably wingless, and their young are hatched almost as fully 

 developed as the adults. They do not undergo metamorphosis, 

 but their growth and development are accompanied by the phe- 

 nomena of skin changing. 



It appears that when the parasitic lice or Pcdiculi — which consti- 

 tute an important portion of the class Anophira — are hatched from 

 the egg, they have not much subsequent alteration to submit to, as 

 they are nearly perfect. Moreover, the young louse is not more 

 perfect than the adult, and, therefore, no retrograde metamorphosis 

 takes place. The caterpillars of Psyche and Orgyia turn either into 

 male moths with beautiful wings or into females with the most 

 rudimentary organs of flight, and this occurs because these last 

 submit to a retrograde metamorphosis. The adult female Orgyia 

 is absolutely lower in organisation than the caterpillar. But, 

 although there is some resemblance between these female moths 

 and the Anophira, it must be remembered that the lice retain 

 their larval condition through life. There are some proofs, how- 

 ever, that there is a retrograde development in the louse before 

 it is hatched. Until late in its life within the (^gg the louse grows, 

 and is formed like the embryos of other insects, and then, just 

 before hatching, takes on its peculiar degraded aspect and essential 



