Mr. G. A. K. Marshall on the Genus Byblia. 335 



Nat. Hist. (6) xviii. p. 73) : — " I believe B. achelo'ia is sup- 

 posed to be the extreme development of the dry-season form 

 [of B. ilithyid] in South Africa. The puzzle to me is, Why 

 should a species common to India and Africa produce totally 

 different varietal forms in the two countries ? As B. vulgaris 

 only occurs in Africa, it can therefore only be supposed that 

 in India the species produces two dry-season forms — B. iliihyia 

 and B. simplexy Upon what foundation this singular 

 belief is based I know not ; but it certainly did not originate 

 in South Africa. It is true that B. achelo'ia^ Wallgr., was 

 founded on dry-season specimens, but it represents the dry 

 form of the variety, usually known under that name, and not 

 the dry form of typical iliihyia, its corresponding wet-season 

 form being B. ilithyia, var. vulgaris^ Staud., which Mr. Butler 

 erroneously considers to be a distinct species. The reasoning 

 contained in the latter half of the above quotation is far too 

 subtle for my comprehension, for I quite fail to perceive that 

 the restriction of a certain variety of iliihyia to the African 

 continent must necessarily imply that in India that species 

 ])roduces only two dry-season forms and no wet-season one. 

 Surely this is but a " lame and impotent conclusion," and 

 were tliere any truth in it, it would be a far greater puzzle 

 than that propounded by Mr. Butler, which latter seems to 

 me but a very simple matter after all. 



The real relation of these various forms is as follows : — 



The type of the species was a wet-season specimen as far as 



can be judged from Drury's somewhat crude iigure, which is 



founded on a West-African example, and Cramer's figure of 



his polynice belongs to the same form. During the dry 



season in Africa the underside assumes a very different 



appearance, the colouring being more or less rich ferruginous, 



with three transverse macular white stripes, viz. subbasal, 



median, and submarginal. Curiously enough this form 



appears to have escaped the infliction of a specific name. In 



India the change is not nearly so marked, but the dry-season 



form has been described under the name of simjAex, Butl. 



Mr. Butler notes that the British Museum specimens of the 



latter form were all caught in February and those of the 



typical form in April, May, and October, which is quite in 



accordance with my contention that they are seasonal forms 



of one species. I am, however, aware that Mr. de Nic^ville, 



in his fine book on the Indian butterflies, records Col. Swinhoe's 



statement that he has taken the simplex form practically all 



the year round, on the strength of which he retained it as a 



distinct species. But in a later paper he unites the two forms 



(Journ. As. Soc. Beng. 1889), for, as he there shows, 



