142 DR. A. G. BUTLER ON SEASONAL [June 7, 



2. On Seasonal Phases in Butferflies. 

 By A. G. Butler, Ph.D., F.L.S., F.Z.S., &c. 



[Received May 10, 1904.] 



The fact that Butterflies emerged from the pupa in markedly 

 different forms at different times of the year was made evident 

 many years since by the labours of W. H . Edwards in the United 

 States, by Mansel Weale in South Africa, and by Doherty and 

 de Niceville in India ; but this fact was misunderstood, and there- 

 fore not fully accepted by many workers for years afterwards, 

 whilst not a few are sceptical as to its truth at the present day. 



One of the chief reasons for this scepticism is based upon the 

 unquestionable truth that the dry-season type of a species not 

 unfrequently emerges in the wet season and vice versa. That I 

 was myself rendered sceptical for years on this ground will be 

 seen by referring to some of my earlier papers in which the 

 question of seasonal forms had to be considered. 



In a paper published in 1884 (P. Z. S. pp. 478-501) I recorded 

 the remarkable fact that, at Aden, Limnas chrysippus, Hypolimnas 

 misippios, and Gatopsilia floreUa produced all their varietal phases 

 simultaneously, and that Teracolus " nouna " = saxetos (which 

 actually is the 1\ evagore of Klug) occurred in March, April, and 

 May, whilst T. yerhurii was also obtained commonly in April 

 and May ; but I did not then fully appreciate the fact that all 

 these were instances of the simultaneous emergence of phases 

 characteristic of seasons and climates, and that they represented 

 the probable condition of all very variable types before seasonal 

 or climatic changes had begun to act ujjon them. 



As with protective mimicry, the more enthusiastic exponents 

 of which have frequently erred in supposing that beca,use this 

 was of use against one enemy, it must necessarily be against all ; 

 so has it been with those who desired to believe in, but failed to 

 compi-ehend, seasonal vaiiation. That I misunderstood it myself 

 in 1886 is clear from the remarks which I made in a paper upon 

 J^pidoptera from Western India (P. Z. S. p. 399) i-especting the 

 broods of Belenois mesentina: in 1888 I was no wiser, as my 

 remarks emphasising the importance of dates of capture in the 

 case of certain species of Teracolus clearly show (Ann. & Mag. 

 Nat. Hist. ser. 6, vol. i. p. 201). 



In 1895 (P. Z. S. p. 727) I hinted at the possibility of Hypan- 

 artia schceneia and H. hippomene being seasonal forms of the 

 same species, and in 1896 (P. Z. S. p. 112) I considered this 

 probable ; yet later in that year (P. Z. S. p. 285) I concluded 

 that this was an error, because both were captured on the same 

 mountain upon two successive days. At this date, therefore, it 

 is quite evident that I considered it impossible for wet and dry 

 phases of any species to occur simultaneously. Indeed, it was 

 only after reflecting upon the probable identity of T. yerhurii 

 with the supposed T. 7iouna (P, Z, S. 1896, p. 247) that I began 



