212 Annals Entomological Society of America [Vol.11, 



and that the most northern forms are larger than the southern in 

 both hemispheres — the probable result of a slower metamorphosis 

 in a more temperate climate. 



Evidence That Daxaida Is Ax Old World Genus That Has 



Invaded the New. 



, The suggestion might perhaps be made that the New World 

 forms of Danaida are the more ancestral, and that those of the 

 Old World have been deri\-ed from them In' migration westward. 

 There is no reason for concluding that the Danaidas of either 

 geographical area possess a more primitive structure than those 

 of the other ; we are therefore driven to consult other lines of evi- 

 dence. The following comparisons clearly indicate that Danaida 

 is an Old World genus which has invaded America at no very 

 remote period: (i) the far larger number of the Old World 

 forms and the greater degree of specialization by which some of 

 them are distinguished; (2) the place of Danaida as one out of a 

 number of nearly related genera making up the Danaini, a large 

 and dominant Old World group, per contra its isolated position in 

 the New World; (3) The highly developed and complex mimetic 

 relationships of the Old World Danaidas. 



This last statement requires some expansion and exemplifi- 

 cation. Allusion has already been made to the resemblances 

 which have grown up between different species of Danaida in the 

 same island, — resemblances in which the forms of chrysippns 

 appear to act as models. Even more striking is the mimetic 

 approach of certain Old World Danaidas to species of the other 

 dominant Oriental section of the Danainae — the Euploeini. 

 Thus in the Solomons, Danaida (SaJatura)' insolata is a beautiful 

 mimic of the dark-white-margined Euploea brenchleyi, while in 

 the same islands Danaida (Salatitra) decipiens mimics the dark, 

 white-spotted Euploea asyllns}- Finally, and most convincing 

 as evidence of long residence, are the numbers of mimics which in 

 the Old World have taken on the superficial appearance of species 

 of Danaida. In addition to the extraordinary degree to which 

 the Mimicry of D. chrysippns is carried in Africa, it is mimicked 

 in the Oriental Region by the females of Hypolimnas misippiis 

 and of Argynnis niphe, and by the males of certain species of 

 Cethosia. Danaida genntia and the forms related to it are also 



>2 See J. C. Moulton in Trans. Ent. Soc. Lond., 1908, 603, 004: PL XXXIV, 

 figs. 5, 10. 



