THE YOUNG NATURALIST. 



53 



IS ZYG^ENA MELILOTI A GOOD SPECIES? 



By W. H. TUGWELL. 



Mr. S. Webb, in Yol. 8, page 224, of this Journal, and in Vol. 9, page 20, 

 pretty clearly stated his opinion that Zygmta meliloti is only a stunted or 

 dwarfed form of Zygcena trifolii, and suggests that this condition has probably 

 been produced by the draining of the locality, by the cuttings of the South 

 Western Railway passing through the New Forest, inferring, that by this 

 drainage, the food-plant of trifolii had possibly become less luxuriant, and 

 consequently had by time produced a smaller and weaker form of Zygcena, 

 which we in error, had styled Z. meliloti, Esp. This at any rate is what I 

 take Mr. Webb's two letters to mean. Not that there is no L. meliloti, Esp, 

 but that our insect is only L. trifolii in a dwarfed state. The genus Zygcena 

 is, I take it, a good instance of what I would call a Darwinian Genera. Our 

 British list gives us four species that certainly run extremely close to each 

 other, and it is no great strain on our belief to imagine that Z, meliloti, 

 trifolii, lonicera, and filipendulce, at no very distant epoch was one species. 

 In a well selected and long series, it would not be difficult to so arrange 

 these four so-called species, that he would be a bold man that would posi- 

 tively group them into four and only distinct species. They run so imper- 

 ceptably one into the other, that to state positively where one species ended 

 and the next commenced, would be a good puzzle to most if not to all of us. 

 It is easy enough to select well defined forms and name them to our entire 

 satisfaction. Yet so long as "what is a species," is not more clearly denned 

 than it is at present. It appears to me convenient to still regard them as 

 four distinct insects, and individually, I consider L. meliloti as distinct as 

 any of them. L. meliloti is not only a much smaller insect than trifolii, but 

 it is as my friend Mr. Gregson tersely puts it " as a race horse to a carriage 

 horse/' Its wing expanse may be and is quite equal to many small examples 

 of L. trifolii, but the wings are narrower, thinner, and much less densely 

 scaled. When in their very finest condidion, they have a semidiaphanous 

 appearance, and always deficient of that dense rich coloration seen on L. tri- 

 folii. In the New Forest, the two insects occur on the same ground, and I 

 can quite believe that in many collections the small New Forest form of 

 trifolii has been sent out by some collectors in error as meliloti, and that, 

 perhaps may occasion the difficulty that Mr. Eobson states has occurred to 

 himself in not being able to distinguish between small trifolii and meliloti. 

 I am certain that if Mr. Robs on saw my series he would have that difficulty re- 

 moved. I candidly admit that some of the New Forest trifolii taken on meli- 

 loti ground run fairly close, but I am disposed to believe that these may be 



