( 189 ) 



XT. Notes on some cases of Seasonal Dimorphism in 

 Butterflies, with an account of Experiments by 

 Mr. G. A. K. Marshall, F.Z.S. By Frederick 

 A. DiXEY, M.A., M.D., F.E.S., Fellow of Wadham 

 College, Oxford. 



[Read March 19th, 1902.] 



Plate IV. 



CONTENTS. 



PAGE 



1. Seasonal Dimorphism in Gatopsilia pomona, Fabr. . . . 189 



2. Seasonal I)unor-ph.mm in Gatopsilia pyranthe, hinn. . . 193 



3. Irregularities of Seasonal Dimorphism in various Genera 194 



4. Experiments and Observations in Seasonal Dimorphism 



conducted by Mr. G. A. K. Marshall, F.Z.S., in the 

 years 1896—1901 199 



5. Summary 216 



1. Seasonal Dimorphism in Catojjsilia 2^omona, Fabr. 



I have long been of opinion, from the examination 

 of many hundred specimens, that no line of specific 

 demarcation can be drawn between Gatopsilia 2^omona, 

 Fabr., and C. crocalc, Cram. This conclusion was based 

 mainly on the fact that, distinct in appearance as typical 

 examples of the two forms undoubtedly are, it is easy 

 to arrange a series of examples showing every possible 

 gradation between the two. The relation between G. 

 pomona and G. crocale so much resembles that between 

 forms which there is reason for regarding as cases of 

 seasonal dimorphism, that I was led to suspect that the 

 dimorphism of G. pomona-crocale might also have a 

 seasonal significance. In 1898 I mentioned my suspicion 

 to Mr. Trimen, showing to. him at the same time a good 

 series, including many transitional forms, of G. p)omoiia, 

 which had been captured near Brisbane in 1897 by T. 

 Batchelor, and presented to the Hope collection by Mr. 

 G. C. Griffiths. This series was noticed by Mr. Trimen in 

 his Presidential Address to the Entomological Society of 

 London, delivered on January 18, 1899, and was con- 

 sidered by him as " lending some probability to the view 



TRANS. ENT. SOC. LOND. 1902. — PART II. (JUNE) 



