1886.] L. de '^iceYille—Life-Eistorij of Satyrinoe. 229 



X.— On the Life-Histonj of certain Calcutta Species of Satyrinoe, with 

 special Reference to the Seasonal Dimorphism alleged to occur in 

 them.— By Lionel de Nice'ville, F. E. S. 



[Eeceived 22nd April ;— Kead 2nd June, 1886.] 

 (With Plate XII.) 



At tlie meeting of this Society held on the 3rd December, 1884, I 

 read a paper on the Butterflies of Calcutta, and exhibited a series of 

 specimens, chiefly appertaining to the subfamily Satyrince. In this paper 

 I expressed the opinion that a very marked seasonal dimorphism occurred 

 in this and other groups of butterflies. I also forwarded the same set of 

 specimens to England, and my friend and colleague, Mr. W. L. Distant, 

 exhibited them at the meeting of the Entomological Society of London 

 for February, 1885. My object in bringing the matter thus prominently 

 to the notice of both Societies was to ascertain from the members if they 

 could throw any light on, or offer any opinion as to, the cause of these 

 species being furnished, on the underside of the wings in the brood or 

 broods (most probably the latter) that are on the wing during the rainy 

 season, with strongly marked and conspicuous ocellated spots, while in 

 the same species, or other species that take their place, during the cold 

 and dry seasons these markings are obsolete or entirely wanting, and 

 the general tone of colouration is much paler and more leaf-like. This 

 expression of opinion may have been somewhat premature so far as the 

 question of the seasonal dimorphism went, which certainly had not at 

 that date been proved ; but certainly not so far as the occurrence of 

 ocellated species in the rains and of non-ocellated ones in the cold and 

 hot seasons is concerned, facts of which I had convinced myself by long 

 previous observation. It may be repeated that the Calcutta year is 

 roughly divisible into a cold season (extending from the middle of 

 October to end of March), a hot season (from April to middle of June), 

 and a wet season or rains (from the middle of June to the middle of 



October) . 



A short discussion followed Mr. Distant's remarks on the specimens 

 exhibited at the Entomological Society of London, but I was sorry to 

 find that no solution of the phenomenon was suggested by the members 

 present. My suggestion was that the obliteration of the ocelli was an 

 advantage to the insects during the cold and hot seasons, as at those 

 times the vegetation is much more scanty and dried up, the insects live 

 chiefly among the grass, and would consequently be easily seen were 

 they not inconspicuously coloured and marked ; while in the rains, the 



