t. lilSTORTATA (cREPUSCULARIa) AND T. CREPUSCULARIA (bIUNDULA1;Ia). 109 



earlier emergence influenced by climate in the first instance, and 

 perpetuated by inheritance, etc.," that I thought he had found the 

 correct solution of the phenomena ; but how is it that T. histDrtata 

 has not ousted, or is not ousting, T. crcpuscularia in the Southern 

 counties ? Mr. South says it has been brought about by favourable 

 environment and climate, but these have not altered in Somerset, 

 Berks and Kent, for long periods. Therefore, T. hiatortata ought, 

 long ago, to have supplanted T. crepuxcidaria in the South, but it has 

 not. The two exist together, and there are no signs of the favoured 

 variety {= bistortata according to South) supplanting the original 

 form (= crcpiificulayia). Yet this process is occurring in Yorkshire and 

 Cheshire, according to Mr. Arkle and my own observations, where the 

 ab. (lelanwrenais is gradually supplanting the pale form of T. cre- 

 puscular i a. Again, if T. bistortata be a variety, it must have been 

 crossed now and again by the parent {crcpuscularia) form, when the 

 dates of emergence permitted, and many intermediate forms ought to 

 be constantly taken in Somerset, Berks and Kent. Y'^et we know 

 such specimens are not taken. Then, again, why should altered 

 colour and facies occur together with a shortened pupal stage in a 

 variety ? The same causes would be acting on the parent form at 

 the same time in the same localities (as they exist together). Why 

 should not the parent form also alter the length of its pupal stage like 

 the so-called variety ? Why should not T. crepuacularia emerge in 

 March in the south of England, if T. bistortata, its supposed 

 variety, does so ? Then, again, is there any record of a variety of any 

 other insect that has ever been supposed to have similarly altered its 

 time of emergence ? 



Mr. Tutt {Ibid, p. 304), in some remarks on what constitutes a 

 species, says:— "The important factor to me seems to be, will the 

 individuals copulate freely in a state of nature*'* to propagate their 

 own particular kind ? If so, however variable the forms may be, I 

 think it is generally recognised that the progeny form but one 

 species." He further enquires whether Mr. South, or any other 

 observer, ever saw, in nature, an undoubted specimen of the early 

 species {bistortata) in copulation with an undoubted specimen of the 

 later species {crcpuscularia). That freshly emerged T. bistortata 

 and T. crejmsctdaria will not copulate has never been proved. On the 

 other hand, I think it highly probable that, under favourable 

 circumstances, they would pair, and that their hybrid offspring would 

 prove fertile. f If Messrs. Butler, Hamm, Robertson, Vivian, Studd, 

 A. H. Jones, or Fenn, who obtain T. bistortata in April, will retard 

 the emergence of some of their specimens, obtainable after the middle 

 of April, I would endeavour to pair them Avith some of my earliest 

 T. crcpuscularia, or I would send the latter, in order that they might 

 attempt to cross them with T. bistortata. I would also suggest the 

 importance of obtaining reciprocal crosses. 

 (To be continued.) 



* It is most important that this should be in a state of nature. Many species 

 hybridise when confined artificially. — Ed. 



t These insects have since been paired by Dr. Hiding and Mr. Bacot, in con- 

 finement, but it proves little: Teste, Smerinthus occllatns + S. populi, Amphidasys 

 strataria + A. bettdaria, Zygaena filipendidae + Z. lonicerae, etc. — Ed. 



