Ca) [xev, xevi, xevii 
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 pupze 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. Pouuton, Dr. T. A. CHapman, Mr. W. E. 
Suarp, Mr. W. J. Lucas, and other Fellows joined in a 
discussion of the spread of melanism in various districts of 
Britain and elsewhere. 
Wednesday, November 2ist, 1906. 
Dr. F. A. Dixey exhibited dry- and wet-season forms of 
both sexes of Zeracolus regina, Trim., together with speci- 
mens of Belenois calypso, Drury, B. thysa, Hopff., MWylothris 
agathina, Cram., and two unnamed forms of Belenois from 
Rhodesia, 
The exhibit was designed to show the strong resemblance 
between the under-side of the wet-season phase of Teracolus 
regina and that of certain forms of Lelenois from the same 
region of Africa—a resemblance believed by the exhibitor to 
be of mimetic significance. He pointed out that between JD. 
calypso and B. thysa, which latter was an acknowledged mimic 
of the distasteful I/ylothris agathina, there existed a fairly 
complete series of transitional forms, one of which at least 
showed on the under-side a striking resemblance to the under- 
side of the wet-season 7. regina. It seemed as if MW. agathina 
