SOCIETIES. 137 
might be divided into three nearly equal causes, viz., heredity, moisture, 
and natural selection. In artificial variation the causes might generally be 
said to be abnormal or diseased; by disease he meant a general weakening 
of the constitution by unnatural influences; the least deviation from natural 
conditions might lead to variation. Mr. Fenn then remarked that the tem- 
perature necessary to alter the colour, viz., 87° to 57° and 57°, alone was 
quite sufficient to put at least all our winter, spring, and autumn insects 
entirely out of action. HH. autumnaria, one of the species relied on, Mr. 
Fenn had had considerable experience in breeding, and in the series he 
exhibited there were many paler and many darker than any shown by Mr. 
Merrifield, and the larvee and pup had been kept under usual conditions, 
and the greater portion of them followed the parent forms. in conclusion, 
he said such variation as was shown by Mr. Merrifield was practically im- 
possible in a state of nature, unless it was the result of disease. Messrs. 
Weir, Adkin, Tugwell, Carrington, Dobson, Barrett, and Tutt continued 
the discussion, the last-named gentleman following Mr. Fenn in attributing 
the variation to disease, and that to a large extent it was caused by prevent- 
ing the proper development and formation of tne colouring pigment. He 
thought the action of temperature was indirect, and produced variation by 
interfering with the normal development. Mr. Merrifield agreed with many 
of Mr. Fenn’s observations, and thought most of them were consistent with 
the results obtained in his experiments, as reported by him. In any case, 
there could be no doubt that, in the species principally operated on by him, 
temperature, applied in such moderation as not to affect the healthy appear- 
ance of the insect, produced great uniformity; conspicuous differences in 
colouring. ‘There were other species in which no considerable effect was 
produced, unless the temperature was so extreme as to cause a certain 
amount of crippling or imperfect development. The meeting closed with a 
vote of thanks to Mr. Merrifield, proposed by Mr. Fenn and seconded by 
Mr. Jenner Weir.—H. W. Barker, Hon. See. 
LancasHIRE AND CHESHIRE ENromotoaicaL Society. — April 11th, 
1892.— 8S. J. Capper, F.L.8., F.E.S., President, in the chair. Messrs. 
W. Webster, of St. Heleus; C. F. Johnson, of Stockport; and the Rey. 
C. J. Buckmaster, of Wigan, were elected members. Mr. J. E. Robson, 
of Hartlepool, editor of the ‘ British Naturalist, read a paper entitled 
“Melanism and its Theories.” After reviewing the various theories of 
previous writers for the tendency of certain species to darken, he said it 
was his belief that no single theory could account for the phenomena of 
melanism now going on; and while agreeing with Lord Walsingham that 
the dark colour of insects in cold and snowy regions was due to that colour 
being most suitable, he also considered that the increase of smoke and dirt 
would, by obscuring the rays of the sun near large tuwns, also tend to pro- 
duce melanism by the laws of natural selection. ‘The paper was illustrated 
by numerous examples of melanic forms of Lepidoptera and Coleoptera ; 
Mr. C. A. Briggs’ very dark Sphinw ligustri; the President’s black 
Boarmia cinctaria and B. roboraria; and Mr. Robson’s very dark Arctia 
menthastri, Odontopera bidentata, and Chortobius pamphilus being specially 
fine; but the little box that attracted most attention contained, side by 
side, Mr. Briggs’ fine variety of Arctia caia, with faint buff-coloured 
markings ou the fore wings, black bicolor-like spots occupying the centre, 
the under wings being all red; and Mr. Capper’s variety of the same 
species, the fore wings of which are immaculate, with the exception of oue 
