720 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY , Vol, XV 11. 



benefited to the exclusion or diminution of the other ; but in evergreen jungle 

 this is not so. If the climate of Mauritius underwent some considerable Change" 

 by the wholesale destruction of the forests, the dry season form would in all 

 probability predominate and perhaps permanently supplant the wet, and this 

 would not be due to natural selection but merely the effect of those obscure, 

 processes which are grouped under the comprehensive term climate. 



The methods I have adopted in the above experiments are, briefly, as follow. 

 For the dry cold and dry heat processes a glass jar was obtained and the air 

 having been exhausted by the ignition of a little rectified spirit the pupse were 

 suspended from the lid, which was then securely fastened down and glued 

 round the edges. 



For the moist cold a piece of muslin was tied over the jar to prevent the 

 moisture from the melting ice coming in direct contact with the pupa), but 

 this was frequently not sufficient, as I often found beads of moisture on them. 

 The jars containing the pupse for cold conditions were kept in an ice box sur- 

 rounded by ice with a self-registering thermometer. For the moist heat 

 no covering was used in order to allow the heated moisture to escape, and for 

 the suspension of a thermometer, a little water was kept at the bottom of the 

 jar and was heated by a lamp beneath the water bath on which both jars, the 

 dry and moist, rested. I should be grateful for any hints which would tend 

 to reduce my high mortality in another series of experiments. 



[Note, — It is to be hoped that Colonel Manders will make some further experiments, as in 

 those which he has s o far conducted he has been so singularly unfortunate that it is difficult 

 to draw any conclusions therefrom. 



In. a climate like that of Mauritius one would naturally not expect any very .'harp demar. 

 cation between the seasons of prevalence of the two forms. 



The rainfall is heavy and well distributed throughout the year so that there is no marked 

 dry season, and the " wet " form is evidently far the most numerous in eight months of the 

 year. Colonel Manders attributes the increasing numbers of the " dry " form in the remain- 

 ing four months to the fact that tVese are the cold months. 



To a stranger, however, it would seem that in a country where the mean temperature does 

 not vary nearly so much as that of Bombay there can be no very marked cold season either, 

 unless the lower temperature is accompanied by a lowering of the relative humidity as in 

 our case. It would be interesting to have the figures of the mean average humidity for the 

 different months. I have tried to obtain them in Bombay without success. 



In one respect, however, I think Colonel Manders is making rather a bold assumption and 

 that is in supposing that the seasonable changes take place in the last few days of 

 pupal life. I would be inclined rather to attribute them to the relative amount of sap nu- 

 triment and pigment in the food plant of the larva. 



So far as my own observations on the companion Indian species, M. ismene, are concerned, 

 1 should say that near Bombay the insect is only really common except in October and early 

 November when it is often excessively abundant both by day and night. 



These-or at any rate the fresh specimens— are all of the " dry " season form, October, I 

 need not say, is one of our hottest months. In the monsoon I have only observed the 

 ocellated form. 



It is a pity that more of our members do not undertake similar experiments to those made 

 by Colonel Manders, and it is to be hoped that the relation of his experiences may 



encourage others to do so. 



L. C. H. YOUNG, 

 Hon. Sec, 

 Entomological Dept., Bo. Nat. Hist.Society.] 



