322 REPORTS ON THE STATE OF SCIEXCE. 



own special cases of melanism, the most recent and noteworthy being the 

 fine purple-black form of IlamerophUa ahruplaria, at present almost 

 confined to North London, The black variety of Eujnthecia rectangulata, 

 black Boarmia rliomhoidaria, and tlie darkest Acronycta psi are largely 

 London forms, though the West Yorkshire Rhomboiclaria (variety 

 Perfitmaria) does strongly approach the London moth. 



A few words on Yorkshire leucochroism, inasmuch as it must be con- 

 sidered in its bearings on local melanism, and we will pass on to the 

 immediate object of our meeting this morning. There is little of it in 

 our county, but with the main tendency so strongly in the opposite 

 direction, why should there be any at all ? 



Perhaps our most remai'kable example is Cularia suffiimnla. A 

 raelanic form of the species, variety piceafa, occurs pretty commonly in 

 Scotland, and ought, judging from all our experience with other species, 

 to be still commoner in West Yorkshire. But it is not — scarcely occurs 

 at all. Indeed, the only West Yorkshire record I know is by Mr. Arthur 

 Whitaker, who found a specimen at Worsbrough, near Barnsley ; and it is 

 almost as rare in the other parts of the county. Tiie tendency of the species 

 is distinctly to become paler. Mr. B. Morley, who for many years has had 

 great expei'ience with the species, puts the matter so very clearly that I can- 

 not do better than quote his remarks. He says : ' ' Last spring I netted a few 

 Snffnmata, using no discrimination whatever, only for those in the bestcondi- 

 tion. In due time, when pinned in the cabinet, the difference in comparison 

 with otliers taken on the same hedgerow seven years ago was very striking 

 indeed. The lighter parts of the wings wei'c more clear, and the central 

 band darker. In the same locality a brighter {i.e., paler) form than this 

 is frequently taken, and very rarely the extreme pale form, variety 

 Porrittii, is obtained also. It seems probable that the extreme form, now 

 so rare, is in reality the forerunner of what the species will become 

 locally. It may be of interest to note that the dark vai-iety Piceafa, which 

 occurs in .some parts of the north of the county, has neven been recorded 

 jiere. One would expect that the dark form would be the natural 

 variation of the specifs in tliis district, Avhere melanism predominates, in 

 comparison with any otlier variation, especially wlien it is remembered 

 that the dark variety V'lreala is by far tlie commonest form of variation 

 in the species in these islands.' the only locality in Britain, besides the 

 West Riding district, where the pale forms are known to occur is Dovei', 

 and it seems unaccountable tliat in so common and widely distributed a 

 species the variety sl»ould not occur between Yorkshire and Lent. 



Another Yorkshire leucochroic species is the familiar pine-frequenting 

 Fidonin piniaria. Here, and indeed throughout the north of Britain, 

 the gi'ound colour f>f tlie wings of the male is pure white, wliereas in the 

 south of England woods it is yellow. The species abounds all over the 

 melanic area of West Yorkshire, yet seems to be absolutely proof against 

 any tendency to darkening. Why is this 1 The same tiling occurs with 

 a somewhat closely allied species, Stvenia claiJirafa, which, however, does 

 not occur in South- West Yorkshire. It is abundant on the coast at 

 Scarborough, the ground colour, in my experience, being always white, 

 whereas in the south of England it is yellow. Yet that there is a 

 tendency in the genus Fidonia to melanism is proved by the common 

 Fidonia atomaria occasionally being black in Soutli-West Yorkshire. 



. > Natvralnt, February 1906, pp. 48-9. 



