398 Mr. G. A. K. Marshall—Some Experiments 
L.—Some Excperiments in Seasonal Dimorphism. 
By Guy A. K. Marswatt, F.Z.8. 
ALTHOUGH a considerable number of important experiments 
to test the direct effects of temperature and humidity upon 
the coloration of butterflies have been carried out by several 
distinguished observers in Hurope, yet the question appears 
to have received but little attention in those parts of the 
tropics where the extreme difference in the seasons has 
resulted in many striking cases of seasonal dimorphism. 
Possibly other experiments in this direction have been placed 
on record, but the only one which has come under my notice 
is that of Doherty with Melanitis leda, where he succeeded in 
producing the wet-season form during the dry season by 
keeping the larve and pupz in a bottle containing a wet 
sponge. The paucity of such records has led me to publish 
the results of a short series of experiments made during the 
past winter with a view to ascertaining how far humidity 
alone, as apart from heat, can be held responsible for the 
marked differences between the summer (wet) and winter 
(dry) broods of many of our butterflies. 
The species used in these experiments belong mostly to 
the genus Terias, the reason for this being, partly, that the 
Jarvee and their food-plants were more accessible than those 
of most other suitable genera, but principally owing to my 
surmise that a species which exhibits a gradual and con- 
tinuous transition from the summer to the winter form would 
probably respond more readily to the direct action of climatic 
conditions than would one in which the intermediate forms 
have been more or less largely eliminated by natural selection, 
and which thus might have acquired through this principle a 
definite alternation of generations, irrespective of external 
stimuli, as first suggested by Weismann. The truth or 
otherwise of this supposition has yet to be demonstrated, 
though the results here set forth do not appear to lend it any 
support. 
The experiments fall into two groups. In the first series 
the larve: were reared under normal room conditions, and 
were not transferred into damp surroundings until they had 
suspended, the only exceptions being two examples of Terzas 
senegalensis which had pupated in the room before being 
submitted to moisture. In the second series the period of 
humid conditions was much lengthened, the larve being kept 
in the damp tins for from five to thirty-six days before pupa- 
tion, in case this might prove to be the more sensitive stage. 
The necessary conditions were obtained by using a number 
