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. 342.—Wings of Bombyx ntori. 
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 Bombycidae, 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- 
