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Saw-fly form, while the larvae of the Lepidoptera more generally 

 resemble the X^^^^o stages of the higher Bees. Hitherto recorded 

 observations suggest that the higher Tracheata have been evolved 

 by an effort of adaptation to a land life. The land was probably 

 visited at first irregularly and then at a stated life-period, while the 

 Hexapodous type affords an ascending series of grade in terrestrial 

 adaptation. The consideration of the general longer period of larval 

 life shows a connection with this effort, while the greater equaliza- 

 tion in duration of the periods of growth, or the curtailment of the 

 younger stage to the benefit of the adult, marks a permanent ad- 

 vance in t}"pe in Hexapoda. 



In examining the general characters offered by the Lepidoptera, 

 attention has been already directed by Agassiz to the position of the 

 wings. The elevation of both pair in the Papilionidae necessitates 

 a single muscular action in the act of assuming flight. In the 

 Moths the primaries being deflexed and the hind wings doubled 

 upon themselves, an additional muscular movement is required 

 and, as I have assured myself, the wings are first independently 

 thrown forward. That the stronger-hued Diurnals are in all proba- 

 bility more recent in time than the Moths, must be, in default of 

 palaeontological evidence, as yet mere surmise ; yet Castnia sug- 

 gests the forms through which the Bombycidous type may have 

 passed. 



The antennae of the Lepidoptera have early enlisted the attention 

 of classificators, but I find on reflection a renewed objection to 

 Boisduval's terras in the physical unimportance of the difference 

 they signalize. On comparing the antennae of the Moths and 

 Butterflies together, we should be rather struck by their rigidity 

 and uniform length in the latter group. The flexibility and 

 diversity of the appendages to the joints of the antennal stem 

 in the Moths, point to a more active use. From the stout, 

 rayed and short antennae of Attacus, to the thread-like, simple 

 and lengthy antennae of Adela, there is a wide diversity, in- 

 dicative of utilitarian change. When we remember the general 

 habit of the Moths, the necessity for a development of their percep- 

 tive faculties, independent of vision, seems obvious; their more 

 sensitive antennae may protect them from many enemies their 

 habit exposes them to. On the other hand the Butterflies arc more 



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