4 1 
cumstances of environment may suggest an alliance. Of course such 
conclusions should not be taken for more than they are worth, but, on 
the other hand, it would not be wise to overlook them altogether. 
I have spent considerable time in pointing out to you the effect 
that temperature experiments have been shown to have on various 
lepidoptera, and the special interest which these experiments have 
when connected with those insects which have marked seasonal dimor¬ 
phism, such as Vanessa prorsa, Chrysophanus plilaeas (in southern 
latitudes), Selenia illustraria, etc., in which pupae, that should have 
produced individuals characteristic of one emergence, have pro¬ 
duced, under special temperature treatment, individuals with the 
character of the other emergence, is, of course, patent. It must not 
be forgotton, however, that just as some of our Palsearctic butterflies 
produce normally two seasonal forms—often called the winter (spring) 
and summer forms—so, in tropical regions, seasonal forms known as 
“wet” and “dry” are quite common, presenting different facies, 
sometimes of colour, more often of ocellation. Our climate, of course, 
is not suitable to the production of this class of seasonal forms, as it 
does not afford the necessary conditions. Yet, since it is so common 
a phenomenon in tropical countries, and it must be conceded that 
moisture is an effective external factor in these instances, it cannot 
be gainsaid that in a moist climate like ours the general effect of this 
factor may be considerable. 
Referring to this subject of dry- and wet-seasonal dimorphism, 
Mr. W. Doherty, in the Journal of the Asiatic Society of Bengal (vol. 
lviii., pt. ii.. No. 1, 1889), records that he succeeded in the early part 
of the dry season, in the island of Sumbawa, in breeding both 
Melanitis leda and M. isrnene, from the eggs of M. leda, by keeping a 
wet sponge in the box in which the form M. leda was being reared 
from larvae. The wet-season form is ocellated and feebly angulated, 
the dry-season form is non-ocellated and angulated. These, strange 
to say, are exactly the differences between the wet and dry season 
forms of the Nymphalid Junonia asterie, the latter being the ocellated 
wet-season form of the non-ocellated dry-season form J. almana. 
It would be useless to wade through the various records of this 
phenomenon as described by Moore and others. I have, however, 
recently been much interested in a perusal of L. de Nic^ville’s 
Butterflies of Sumatra, and was much struck with the fact that he 
found many species which produced dry and wet seasonal forms in 
India and Ceylon, not to do so in Sumatra. Thus, he records, 
among the Satyrids, that Mycalesis medus never develops the dry-season 
form runeka, Moore, which is found in India; the Indian dry-season 
form M. perseus is not known in Sumatra, only the wet-season form, 
blasius, occurring there, neither is there any dry-season form of 
M. minem in Sumatra. Another interesting fact is that the Pierids, 
Terias hecabe and Catopsilia pyranthe, both of which species produce 
distinctly dry- and wet-season forms in India, have the dry- and wet- 
season forms occurring together in Sumatra, and without reference to 
the humidity of the atmosphere, whilst another Pierid, Huphina 
nerissa, the Indian forms of which are generally known as H. phyrne , 
exhibits considerable variation in some localities, the aberrations 
separating off into dry- and wet-seasonal forms, in all localities where 
