202 



THE STUDY OF INSECTS. 



what has taken place with the butterflies, the skippers, and certain 

 moths With these insects the humeral angle of the hind wing has 

 been greatly enlarged, so that it projects far beneath the fore wing 

 (Fig 241). When this has taken place there is no longer any need 

 of a frenulum, and consequently this organ is no longer preserved by 

 natural selection. We find, therefore, that several families of Lepi- 

 doptera that belong to the suborder Frenatse, being descendants of 



VIII 

 FIG. 242. Wings of Bombyx mori, 



ancient frenulum-bearing moths, no longer possess a frenulum. 

 These are classed in the following synopsis as the frenulum-losers. 

 It is a very interesting fact, and one that bears out the theory 

 just stated, that in the more generalized of the frenulum-losing 

 moths, as the Bombycidse, the frenulum has not yet entirely dis- 

 appeared, but is preserved in a rudimentary state (Fig. 242). We 

 place the frenulum-losers last in a serial arrangement of the fami- 



