218 Dr. F. A. Dixey on Seasonal Dimorphism, etc. 



gotzius (including B. vulgaris) is specifically distinct from 

 B. ilithyia. 



In conclusion, I wish to thank the authorities of tlie 

 British Museum of Natural History-, particularly Dr. 

 Butler and Mr. Heron, for help that has always been 

 courteously and readily given. My obligations to Professor 

 Poulton are still more weighty ; I owe to him the enjoy- 

 ment of complete facilities for work in the Hope Depart- 

 ment at Oxford, the loan of Mr. Marshall's letters, and the 

 photographs of specimens that illustrate this paper. With 

 regard to Mr. Marshall himself, I should wish to place on 

 record my sense of the high value of his work as collector, 

 experimenter and observer. He has had good opportunities, 

 Avhich he has known how to use in a thoroughly scientific 

 manner. Moreover, what he has already achieved justifies 

 us in looking for still greater results from his persevering 

 labours. 



Explanation of Plate IV. 



Fig. 1 (underside). Byhlia ilithyia, Drury. A -vvet-scason female. 



2 (underside). Offspring of the above. An intermediate female, 



approaching the "dry " foini wliich corresponds to the Indian 

 B. si7)iplex, Bntl. 



3 (underside). Byhlia gotzius, Herbst. A wet-season female, of 



the form vulgaris, Staud. 



4 (underside). Oftspring of tlie above. A dry-season male, of the 



form achcloia, "Wallgrn. 



(See pages 211, 215.) 



5, 5a (underside). Teracolus achinc, Cram. A wet-season female. 



6, &a (underside). Offspring of the above. A dry-season female 



of the form described by Trimen as antevijjpe, Boisd. 



7, 7a (underside). Tcracolns omphale, Godt. A wet-season female. 



8, Srt (underside). Offspring of the above. A dry-season female, 



of the form described 1)y Trimen as throgonc, Boisd. 

 (See pages 210 211.) 



9, Oc« (underside). Terias scncgalcnsis, Boisd. A wet-season female. 



10, lOrt (underside). Offspring of the above, A dry -season male, 



of the form xthiopica, Trimen. 



(See page 215.) 



In the actual specimens, owing to the ])rcsence of colour, the difference 

 between the wet- and dry-season forms of the same .siiecies is more striking 

 than appears in the Plate. 



