595.78 390 



III 



The Neuration of Rhopalocera 



GIVEN the theory of evolution, structural characters of living 

 insects, whether embryological or imaginal, afford means of 

 classification according to the persistence among them of various 

 degrees of specialization from primaeval forms of structure, i.e. the 

 links of continuity of specialization in any direction. The neura- 

 tion of the wings is a structural character common to all Lepidoptera 

 — a few apterous females excepted. Hepialides and Micropterygides, 

 perhaps the most ancient groups of Lepidoptera now existing, have 

 more wing nervures than any other group and associate the Lepi- 

 doptera with Trichoptera ; series of gradations in modification of 

 neuration in different directions more or less connected (less con- 

 nected, perhaps, among ancient than recent groups), may be 

 observed everywhere among existing Lepidoptera ; thus reduction in 

 the number of nervures, or alteration in the position of certain 

 nervures, connect generalized (ancient) and specialized (recent) 

 forms of neuration ; as a matter of observation, I believe that, 

 nervures once lost, or the position altered, neither has ever been 

 regained — hence the different series of gradations. 



Fore and hind wings corresponding, the neuration may be referred 

 to as follows: — Costa = upper margin. (1) Subcostal nervure. (2) 

 Radial system = nervure with branches. (3) Median system = 

 nervure with branches (nervules). (4) Cubital system = nervure 

 with branches (nervules). (5) Anal nervures = several simple 

 (unbranched) separate nervures. 



In this paper I propose mainly to refer to the neuration of the 

 forewings, and possibly shall not enumerate all the nervures of the 

 wings to save unnecessary details. 



Cossids, so far as I know, cannot be considered in any way 

 related to the Ehopalocera, except by connections too remote to 

 trace ; they retain a neuration relatively more ancient than that of 

 any group of Ehopalocera. 



It may be instructive to compare the Cossid form of neuration 

 with the several more or less definite forms representing several 

 groups of genera in the Ehopalocera, and I may here say that by the 

 term group I mean an assemblage of species which may be associated 

 upon a given pattern of wing neuration, or a distinctly connected 

 modification of the same. In a recent instructive paper upon the 

 " Classification of the Day Butterflies," published January and Feb- 

 ruary 1898 in Natural Science, Dr Eadcliffe Grote has given details of 



