T. BISTORTATA (cREPUSCULARIa) AND T. CRfiPUSCULARIA (bIUNDULARIA). 31 



the brown ercinvtc^daria is obvioudij biundularia." You have before 

 you to-night probably the most extensive series of these species ever 

 made in Britain. I ask you whether their characters are not patent. 

 I have, for the sake of expediency, referred continuously in this 

 paper to the first brood of T. crepuscularia as the ochreous form, to 

 the second brood of T. crepuscularia as the dull white-grey form, and 

 to T. biundularia as the paler species, and in a general way these 

 definitions are true, and we could add to these the typical form of 

 crepuscularia ( = bistortata, Goetze) as represented by the German and 

 Perth insects as the fuscous or umber-brown form. But these 

 are all comparative terms at the best. There are white, ochreous 

 fuscous, and black (-brown) crepuscularia. There are white, ochreous, 

 and black T. biundularia. The whitest crepuscidaria are absolutely 

 whiter than the whitest biundularia, and it is possible to find some 

 biundularia more ochreous than some crepuscularia, but parallelism of 

 colour variation is not sufiicient to unite, as one species, insects with 

 distinct and separate life-cycles, and there is no more logic in uniting 

 Afirutis cursor ia and A. tritici as one species, because I disagree with 

 Mr. Barrett as to the exact locus of a particular aberration of what we 

 know must be one of these species, or, in uniting Cidaria immanata 

 and C. rmsata, because a certain aberration would be differently 

 placed by Mr. Fenn and luyself, than in uniting T. crepuscidaria and 

 T. biundularia, because Mr. Barrett fails to place an aberration from 

 Derbyshire, or German specimens which represent a race (of one of 

 the two species) with which he was entirely unfamiliar. For this 

 reason, I leave out of account entirely the parallel dark aberra- 

 tions of the two species which require training to locate, but, given 

 time and practice, I have no doubt many lepidopterists will locate 

 these as certainly as can Mr. Prout, Major Kobertson and other keen 

 and practical entomologists. 



In taking leave of the aberrations of these species in this summary 

 way, I would insist that, apart from the melanic aberrations that both 

 species present, T. crepuscularia is (as asserted by Doubleday, Chappell, 

 and others, and negatived by Mr. Smallwood) distinctly the darker 

 species. 



The rest of my note must necessarily be brief. Although I have 

 throughout considered and spoken of T. crepuscidaria as the early 

 species, and given its dates of appearance as March and April, yet 

 much necessarily depends upon the season. In 1893, it was recorded 

 the last week in February, and in 1888, by Mr. C. G. Griffiths, on 

 May 5th. In 1893, T. biundidaria was out by the second week in 

 April, in 1888 it was not out until late June, and occurred even into 

 July. To compare the April emergence of T. biundtdaria in 1893 

 with the May emergence of T. crepuscularia in 1888, is obviously 

 useless and absurd, but that is what is repeatedly done, the date 

 of appearance of biundidaria in one year, compared with the date 

 of appearance of T. crepuscularia in another, and vice versa (see 

 Entom., xix., p. 270, and E.M.M., xxiii., pp. 41-42). The second brood 

 of T. crepuscidaria was out, in 1896, before the date at which 

 biundularia occurred in 1888, but this does not vitiate the broad 

 principle nor weaken the general argument. Each year must be 

 taken by itself, and the relative time of appearance will usually show 

 a clear four or five weeks between the first emergence of T. crepuscu- 



