Seasonal Dimorphism in Butterflies. 195 



experience of Mr. Marshall, who in April 1898 bred a 

 specimen of Precis sesamus and another of F. octavia-nata- 

 lensis from two eggs, laid on the same day by the same 

 mother, and reared under precisely similar conditions.* 

 Dr. Butler has also put it on record that Captain Nurse 

 bred Teracolus yerhurii, Swinh., and T. nonna, Luc.,f from 

 a batch of similar larvte, the perfect insects presumably 

 emerging at the same season. Many cases have been 

 observed where, although each of the two forms of a 

 species is on the whole confined to its own time of year, 

 there is yet a considerable amount of overlapping at 

 the change of seasons ; this overlapping showing itself 

 both by the simultaneous occurrence of freshly-emerged 

 specimens of both phases, and also by the appearance of a 

 more or less complete series of " intermediates." A good 

 instance of the simultaneous occurrence, in the field, of 

 different phases believed on strong grounds to be seasonal, 

 is afforded by the capture of all three forms (" wet," " dry," 

 and " intermediate ") of Precis sesamus by Mr. Crawshay at 

 Nairobi within little more than a week during the month 

 of April. J Many records of this kind are in existence; 

 and are often, no doubt, to be ranked as examples of the 

 seasonal overlapping that has just been mentioned. 



It is however evident that there are numerous cases of 

 simultaneous occurrence which cannot be brought under 

 this head. Besides the definite statements of de Niceville 

 with regard to two species of Catopsilia, we have now a 

 considerable bulk of evidence, with regard to many species, 

 of the appearance side-by-side, at all times of year, of 

 forms closely analogous with what are now well established 

 as seasonal phases. Thus, again according to de Nice- 

 ville, the ocellated and non-ocellated forms of Ifelanitis 

 leda,, Linn., which he has shown to be related in India to 

 the wet and dry seasons resj^ectively, both occur in North- 

 East Sumatra all the year round. In Java it has been 



* Ann. Mag. Nat. Hist., 1898, vol. ii, p. 30. 



t More accurately, perhaps, T. evagore, King. T. nouna is the 

 dry-season phase of tlie African form T. dairn, King. Capt. Nurse's 

 larvae were found at Shaik Othman, and no doubt belonged to the 

 Arabian form, of which T. yerhurii, Swinh., is the wet, and T. 

 evagore, King, the dry-season pluise. This is pointed out by Butler 

 in Ann. Mag. Nat. Hist., 1897, vol. ii, p. 460. The original record 

 is in Proc. Zool. Soc, 1896, p. 247. 



X Proc. Zool. Soc, 1900, p. 916. 



TKANS. ENT. SOC. LOND. 1902. — PART II. (JUNE) 14 



