( xcv ) 



point to the fact that it is such enemies as attack butterflies at 

 rest (for example, lizards) that are especially dangerous during 

 the drier part of the year. 



" Whether the duskiness so often met with in arctic and 

 mountain forms can at present be explained as an adaptation, 

 is perhaps doubtful ; though there seems to be no reason why 

 Lord Walsingham's suggestion of its relation to the power of 

 heat-absorption should not be correct. In such cases of the 

 development of dark pigment as we see in females of Mijlothris 

 lorena, Hew., M. jyyrrha, Fabr., Pieris demophile, Clerck., 

 P. viardi, Boisd., P. locusta, Feld., P. tithoreides, Butl., etc., 

 to which may probably be added the wet-season Glutophrissa 

 saha $ (see Trimen, Proc. Ent. Soc. Lond., 1881, p. viii), the 

 influence at work is that of mimicry, and the result clearly 

 takes rank as an adaptation. 



" The occasional predominance of dark pigment in the males 

 as compared with their mates is apt to show itself in the form 

 of distinct and definite areas — not in that of suffusion. A 

 common effect therefore on the male is to make that sex not 

 less, but more conspicuous. Hence the pigmental areas may 

 possibly in these cases serve as recognition-marks. 



" This last, however, is but a suggestion. I am far from 

 saying that the advantage of a melanic tendency to its possessor 

 is in every instance demonstrable. I only submit that our 

 present knowledge, so far as it goes, points to selective adapta- 

 tion as the principle which seems likely to cover most if not 

 all of the diverse conditions now grouped together under the 

 comprehensive head of melanism." 



The President said he thought there was no doubt that 

 temperature had, what appeared to be, a direct effect in the 

 case of many Lepidoptera. For example, on many of the 

 common Geometrid moths, if the pupse were exposed, some to 

 a temperature of 40° to 50°, others to one of 70° to 80°, those 

 at the lower temperature were darker. 



Professor E. B. Poulton, Dr. T. A. Chapman, Mr. W. E. 

 Sharp, Mr. W. J. Lucas, and other Fellows joined in a 

 discussion of the spread of melanism in various districts of 

 Britain and elsewhere. 



