INTRODUCTORY. 



15 



been pleased to term " nervures." It results 

 from a careful examination of the writings 

 of entomologists, that exactly one third have 

 described these supports as "veins," exactly 

 one third as " nerves," and exactly one third as 

 " nervures," or '' nervules "; the advocates for 

 each term having shown to their own entire 

 satisfaction its peculiar and exclusive propriety. 

 The argument always runs thus : " We know 

 very well that these organs are not veins (or 

 ' nerves', or ' nervures,' as the case may be), 

 but it is a matter of convenience so to deno- 

 minate them ; and no sensible man will deny 

 the advantages of a uniformity in anatomical 

 nomenclature." This reasoning appears to 

 me somewhat illogical: if we "know very 

 well " that the wing of a bird is not a leg, it 

 can be no convenience to any one to call it a 

 leg ; if we " know very well " that the head 

 of a horse is not its tail, it really can be no 

 convenience to call it a tail. "We know 

 exactly the use and object of these supports : 

 it is precisely the same as that of the fin-rays 

 of a fish, which are invariably called " rays," 

 and therefore, wherever I have had occasion 

 to mention these rays, either in the present 

 " history," or in that previously published of 



the " British Moths," I have invariably called 

 them " rays " a term which I venture to 

 hope all my readers will accept, since they 

 cannot fail to understand. 



EXPLANATION OF TERMS. 



With the single exception of wing rays, 

 which my readers will please to understand 

 as precisely equivalent to the fin-rays of 

 fishes, I shall use no terms except those of 

 universal acceptation when speakingor writing 

 of insects ; and I could wish that I had no 

 occasion to use a single word that could not 

 be found in Johnson's Dictionary ; but this is 

 very difficult, and I find, after every endeavour 

 to avoid the use of new words, or of applying 

 new meanings to old words, I am absolutely 

 compelled to do that which I have the most 

 anxious desire to avoid. It is no common 

 achievement to have removed so many of those 

 stumbling-blocks to the acquisition of scientific 

 knowledge italics, abbreviations, and signs ; 

 this is happily accomplished, and we must, 

 content ourselves therewith, and not quarrel 

 over a few unusual words, but endeavour to 

 make them both familiar and intelligible. 



Explanatory Figure of a Butterfly. 



In order that the terms used in describing 

 may be rendered as intelligible as possible, I 



have drawn the outline figure of a butterfly, 

 and indicated by letters the different parts I 



