148 LEPIDOPTEEA INDICA. 



In the Jotirn. Asiat. Soc. Bengal, 1885, p. 39, Mr. de JSTiceville further says, 

 " The constancy of this phenomenon is such that I cannot help thinking there must 

 be some physical reason for it, — can it be a protective one ? The difference in the 

 garb of the surrounding vegetation makes it little remarkable that a change should 

 be found in the coloration of the butterflies of the two seasons, but it is difficult to 

 see why this change should show itself in the obliteration or development of ocelli. 

 The only hypothesis which I can suggest is, that during the rains the density of 

 the vegetation is such that the butterflies can easily hide their conspicuous ocelli, 

 ■while in the cold and dry seasons the ocelli, easily seen through the scantily-clothed 

 jungle, would render the butterflies an easy prey to their inveterate enemies the 

 birds, lizards, and insectivorous insects ; so that the ocellation being a cause of 

 danger would have a worse chance of survival, and consequently would be gradually 

 wiped out by a process of a survival of the fittest, the fittest in this case being the 

 least gaudily-marked individuals. Were this the case, however, the non-marked 

 forms would certainly survive during the rains, for their homeliness of coloration, 

 though no longer absolutely essential, would still give them an advantage over their 

 ocellated brethren, unless indeed the ocelli are preserved by sexual selection at 

 this time when the struggle for bare existence is not so keen as at other seasons." 



In a subsequent paper (Journ. Asiat. Soc. Bengal, 1886, p. 229), Mr. deMceville 

 gives the life history of certain species of Calcutta Satyringe, of the genera Mycalesis, 

 YptMma, and Melanitis, and states that he has "been able to prove by breeding 

 direct from the e^gg, that the extraordinary seasonal dimorphism which he had 

 previously suspected to occur does actually exist," and gives the details of the 

 rearing of the species therein described, which, up to that date, he had suceeeded in 

 obtaining for breeding. The life history of these dimorphic species will be found 

 described under the genera above referred to. 



Later on Mr. de Niceville writes (Journ. Asiat. Soc. Bengal, 1888, 273), " With 

 regard to many of the Indian Satyrinse, they are divided into two strongly-marked 

 well-defined groups, which I have designated dry and wet-season forms respectively. 

 These forms iwevail during their respective seasons, but are by no means strictly 

 confined to them. For instance, it is a common occurrence in India to have what is 

 called a ' break in the rains,' when for many successive days the weather is some- 

 what similar to that obtaining in the dry season. It may be noted that the 

 Calcutta year is roughly divisible into a cold season, extending from the middle of 

 October to end of March; a hot season, extending from April to middle of June; 

 and a wet season or rains, from the middle of J une to the middle of October. Any 

 larv£e turning to pupse during a ' break ' would almost certainly, though they 

 would emerge perhaps a week afterwards in a deluge of rain, be of the dry season 

 form. Similarly, during the dry season, dry season forms prevail, but, should a 



