138 THE ENTOMOLOGIST. 



name. I believe this to be the case with the genus Melitaa, and 

 pre-eminently so with that group of it associated with athalia 

 so that there will remain for generations to come a difficulty, 

 no doubt in time a decreasing one, in finding differentiating 

 characters between the species which will hold good in every in- 

 stance ; nor must we even be surprised if we find individual 

 members of one species (when circumstances, such as rearing 

 from one batch of ova, leave no room for doubt as to their 

 identity) occasionally exhibiting one or more of the very cha- 

 racters which we are accustomed to regard as distinctive of 

 another species, the whole genus being still in a condition of 

 flux sufficient to lead to frequent instances of atavism. It is not 

 then with any expectation of finding unerring rules by which it 

 can be decided in all cases : " this is parthenie ; that is athalia ; 

 this deione," and so forth, that I venture to publish the results of 

 my studies in this group — studies extending over many years 

 in the field and amongst collections, and over months among 

 books — for I believe this to be in the nature of things impossible ; 

 all that I can hope for is to show by what distinguishing marks 

 the various species may, as a rule, be recognized, and by 

 adducing as large a number of these as I can find for each 

 species, to make it more unlikely that all will be found, even in 

 the most aberrant examples of another species than that to which 

 they normally belong. Incidentally I hope to rouse an interest in 

 the great biological question involved, in some collectors whose 

 attention has not been attracted previously in that direction. 



To make our enquiry as exhaustive as may be, it seems 

 necessary to go back to the original descriptions and to trace the 

 way in which the various species have gradually been recognized 

 as distinct. Linnaeus, in the tenth edition of his ' Systema 

 Naturae,' published in 1758, includes all the Melitffiid forms 

 known to him, with the exception of maturna in his description 

 of cinxia, which reads as follows: " Papilio alls dentatis fulvis, 

 nigro variegatis, subtus fasciis tribus flavis." Four years later 

 Geoffroy, in his * Histoire abr6g6e des Insectes qui se trouvent aux 

 environs de Paris,' 1762, first separated them into " varieties," 

 which he thus characterizes : — 



1. " Papilio alls dentatis fulvis, nigro maculatis, subtus 

 fasciis tribus flavis." 



2. The same, except " nigro reticulatis " instead of maculatis. 



3. The same, except "nigro reticulatis et piinctatis." 



4. " Papilio alls dentatis fulvis, nigro reticulatis et punctatis, 

 utrinque fasciis tribus flavis." 



The next step was taken by Rottemburg (' Naturforscher,' 

 vol. vi. p. 5, 1775), who named these " varieties," and recognized 

 them as distinct species, and from him we get the names atJtalia 

 as applied to the second, and aurinia as applied to the fourth. 

 The first and third he calls respectively cinxia and pilosella. For 



