1914.] NATURAL SCIENCES OF PHILADELPHIA. 179 



flourishes prosperously, it is unlikely that a mimetic form would arise 

 from it, this is an objection which at once arises wh(>n mimicry is 

 studied in the original monograph of its founder, published long 

 before Fritz Miiller had thought of his hypothesis. According to 

 Bates, mimicry was a refuge for the destitute, a last means of escape 

 for a hard-pressed and dying species. It was this very conclusion 

 which was Miiller's stumbling-block; for the majority of the mimics 

 in southeast Brazil where he lived were clearly successful and 

 abundant species, and the same is true of the majority of mimicking 

 species wherever they are thoroughly known. Nor is there any reason 

 to suppose that these successful forms originally arose from rare and 

 hard-pressed non-mimetic ancestors. Want of space prevents the dis- 

 cussion of more than a single example. I refer to Tirumala (Melinda) 

 formosa, an Oriental invader into the Ethiopian Region (18, 31). 

 This species, abundant east of the Victoria Nyanza, near Nairol)i, 

 is there beautifully mimicked by the Ethiopian Papilio rex. The 

 invading Danaine has transformed an indigenous species just as in 

 North America. West of the great lake T. formosa is represented by 

 an equally flourishing daughter species, T. mercedonia, with a pattern 

 darker than its parent and one much further removed from the allied 

 Oriental Danaince. Papilio rex west of the lake becomes P. mimeticus, 

 as beautiful a mimic of T. mercedonia as rex is of formosa. The two 

 Danaine models are now distinct species, but their Papilionine 

 mimics, connected by intermediates (P. commixtus) in the interme- 

 diate geographical area northeast of the Victoria Nyanza, are 

 certainly a single interbreeding community. Similarly, in North 

 America Danaida plexippus is a very distinct species from D. berenice 

 and D. strigosa, although these latter may be geographical races of 

 one species. The three forms of Limenitis are, on the other hand, 

 all probably mimetic modifications of a single species, although 

 L. obsoleta is probably distinct from archippus and floridensis. To con- 

 tinue the history of the African invading Danaines: Further 

 westward the flourishing and prosperous T. mercedonia has given rise 

 to a still darker species, T. morgeni, which has altogether lost the 

 appearance of an Oriental Tirumala and has become the most 

 perfect mimic of the African Danaine genus Amauris. 



Here, then, we have a species so dominant that it is mimicked by a 

 butterfly of a different family. It gives rise to another species and 

 the mimic undergoes corresponding changes. Finally, in spite of 

 these evidences of prosperity, it becomes itself a singularly perfect 

 mimic. All these changes are far less abrupt than that from arthemis 



