27 
data for the last year or two with the object of ascertaining the extent 
to which melanism in lepidoptera in this country is progressing or 
otherwise. This is a most particularly interesting question, and I 
hope our Society has not been backward in supplying information. 
Although I had schedules sent to me for the purpose of giving 
statistics, I found that my collecting was too spasmodic to be of any 
service in that direction. Nevertheless, a collector may have a very 
shrewd opinion without being in a position to give statistical results. 
When we view the increasing additions of melanic forms in different 
insects in our cabinets, it appears to me that we can only arrive at one 
conclusion. It can hardly be owing to keener collectors than of old 
that these forms have been discovered in more abundance, but that 
the dark forms are becoming more and more frequent in those species 
that have already shown that tendency, and also, in further develop¬ 
ment in the same direction, in other species. It was in May, 1897, 
that I took the first Pachys betularia var. doubleday aria that I had ever 
seen in the London district. Since then I have met with it twice, 
and I hear from friends that it is no uncommon thing to take them 
at electric light in my own neighbourhood (Forest Gate). 
It is true that many of our cabinet specimens of melanic forms are 
due to breeding by selection, particularly one of our last additions— 
Gonodontis bidentata ab. nigra. The causes of this tendency to darken, 
or, perhaps, I should say this spontaneous development of dark forms, 
has been freely dealt with by abler hands than mine, but there is no 
doubt of the fact that a large number of insects are more dark in the 
north than in the south, some of the most noticeable being Spilosoma 
menthastri, Kupethecia venosata, Perigoma albulata, Mesoleuca bicolorata, 
Melanippe jiuctuata,Xylena monoglypha,Agrotis lucernea,Triphaena cornea, 
Amathes glareosa, A. primulae (= festiva ), A. xanthographa, Dianthoecia 
conspersa, Cleoceris viminalis, and also Hepialus humuli, and it would 
appear to the ordinary observer that these dark forms can only be 
produced by climatic influence. In this list it is difficult to attribute 
the dark colour to protective resemblance, as all the species are taken 
in the south of England in various localities, and quite as freely as 
they occur in the north, but in only one or two exceptions have any 
dark forms occurred in the south. It is true that a somewhat intricate 
theory has been advanced as to the reason which causes the var. in 
H. humuli; but my humble opinion is that the same reason that causes 
the strength of coloration in the above list of species acts on PL. humuli 
and produces that beautiful ab. known as hethlandica. But it is in 
species such as Synopsia abruptaria, Phigalia pedaria, Pachys betularia, 
Cymatophora repandata, Gonodontis bidentata, Tephrosia biundularia, 
T. crepuscularia that the apparent increase in dark forms has occurred, 
and the causes are too subtle to be easy of explanation. Take, for 
instance, S. abruptaria. I have known that insect as a London species 
certainly for the last 40 years, and it is only within recent years that 
the dark ab. has been taken at all freely, and one can hardly imagine 
that London now is so much dirtier than it was 40 years ago that the 
insects have assumed another tint of colour to avoid extermination. 
In a similar manner the same remarks may be applied to P. betularia. 
In the case of this species, the black forms are not only confined to 
the towns, but to my knowledge are now found in the country districts 
of Norfolk, far away from any manufacturing centre. The thought 
