4^^ AND "^^^ 



JOURNAL OF VARIATION. 



Vol. VIII. No. 12. December 15th, 1896. 



A critical resume of the arguments for and against Tephrosia 



bistortata (crepuscularia) and Tephrosia crepuscularia (biundularia) 



being considered distinct species/-^ 



By J. W. TUTT, F.E.S. 



In his recent paper on " The Tephrosia tangle " {Rnt. Rec, 

 vol. viii., pp. 76-81), Mr. Prout has shown most conclusively that, of 

 our two closely allied species of Tephrosia, the earlier and more or 

 less double-brooded species should be called T. bistortata, Goetze, the 

 later and single-brooded species, T. crepuscularia. I need not point 

 out that previously T. bistortata was known as crepmscularia, and 

 T. crepuscularia as biundularia. 



Whether are Tephrosia bistortata and T. crepuscularia two or one 

 species ? This is a question that has been repeatedly asked and 

 answered, and it is almost needless for me to say that there is a 

 remarkable unanimity in the minds of British lepidopterists whose 

 opinions are worth having, that they are two, and not one 

 species. Only three lepidopterists of repute have taken a dis- 

 tinctly opposite view, viz., the Rev. CI. A. Small wood, Mr. R. South 

 and Mr. C. G. Barrett. 



The discussions relating to this matter are now becoming somewhat 

 absurd. The whole principle involved, so far as it has any scientific 

 bearing, is purely a matter of definition. Mr. C. G. Barrett, who has 

 repeatedly raised the question of their specific identity during recent 

 years, has never defined his position. If, in his opinion, a " species" 

 can consist of " two distinct races, each with a distinct life-cycle, 

 each with a distinct facies, and one of them presenting, in addition, 

 marked seasonal dimorphism," then we shall agree with him that 

 these may be but one species ; but, if he considers that every group 

 of insects with a distinct life-cycle that breeds true to its own group, 

 has a separate time of appearance, and, therefore, does not normally 

 hybridise with the members of any other group, constitutes a species, 

 then there can be no doubt that he is in an utterly illogical position in 

 maintaining that Tephrosia bistortata and 1\ crepuscularia are one 

 species. 



The progress of science has taught us that, however distinct certain 

 species may be, others must always be in a state of flux, dependent on 

 the degree of evolution they have undergone. These closely allied and 



* Paper read before the South London Entomological and Natural History 

 Society, October 22nd, 1896. 



