The Genus Melitsea. 



By the Rev. G. Wheeler, M.A., F.Z.S., F.'E.S.—Pwad February 



12th, 1914. 



Human memory is proverbially short, but it may perhaps be 

 within the recollection of those members of the Society who read 

 the " Entomologist," that between June, 1908, and December, 1911, 1 

 wrote in that magazine a paper, extending over 25 numbers, on one 

 group of the Genus we are to consider this evening, viz., that group 

 of which athalia may be taken as representative. 



At the beginning of that paper, after referring to the almost 

 insuperable difficulty of separating the species in that group, and of 

 naming all specimens correctly, I observed : — " For this difficulty 

 two principal causes are responsible : first, the close resemblance 

 inter sc of the ditierent species, and, secondly, the very great range 

 of variation in each species, though always within certain definite 

 limits. But it is the combination of these two difficulties which 

 makes this group of almost unequalled biological interest amongst 

 European butterflies ; for we have here exactly the condition of 

 things which was long ago laid down by Darwin ('Origin of Species,' 

 chap, ii.) as that in which it is easiest to see species as it were in 

 the making. If species have been evolved from previously existing 

 ones, it would be a most remarkable circumstance if we could find 

 no examples of the process taking place under our eyes ; yet the 

 majority of collectors (if not even of naturalists) who give an un- 

 heiitating assent to some theory of evolution, seem to expect to find 

 it possible in all cases to say with certainty to what species any 

 given insect belongs ; disregarding in practice the possibility, nay, 

 the extreme probability, that amongst the number of the European 

 butterflies, many of which are very variable, some few may be ex- 

 pected to exhibit the process of species-making, or, in other words, 

 to afford instances of species not yet absolutely differentiated from 

 each other, and to certain individuals of which it is therefore im- 

 possible to assign with certainty the correct name. I believe this 

 to be the case with the genus Melittra, 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 instance ; nor must we even be surprised if 

 we find individual members of one species (when circumstances, 



