FLETCHER— LEPIDOPTEKA. 321 



It seems probable that the small intiuenoe of currents in the dispersal of the 

 Lepidoptera is directly due to the length of time involved by this process, whereby ova 

 or pupae are practically certain to have emerged en route before accomplishing any great 

 distance. 



Birds may almost be omitted as a factor in the dispersal of the Lepidoptera except in 

 so far as they carry some seeds and thus help to prepare the islands for the support of 

 insects. A small Tineid moth, however, which was found in Cargados Carajos and which 

 seemed to be associated with the sea-birds there, its larva probably feeding on their 

 feathers or excrement, might possibly be transported in the egg state on their 

 feathers. 



Land-birds may also be agents in the distribution of insects, but in the case of remote 

 islands I think they may be left out of account, as they seem to be dispersed mainly by 

 winds and storms, which would be adequate in themselves to carry small forms of 

 life. 



Unman Agency is an important factor, and of the species under present consideration 

 we may say with some certainty that the following have been introduced into these 

 islands by man, viz. : — Corey ra cephalonica, Ephestia cautella, Fyralis manihotalis and 

 P. farinalis. 



VII. On Widely Distributed Poems of Lepidoptera. 



One point which is clearly brought out in the Distribution-Table is the extremely large 

 number of species (39 out of a total of 149, or 26 per cent.) which occur at the same time 

 in the African, Indian, and Australian Hegions. The usual observation, of course, is that 

 these are common and widely distributed species ; but this seems rather to avoid the 

 question, which is really : How does it happen that these species are so widely distributed? 

 Of these 39 no less than 16 are Pyralids and Pterophorids, and although three or four of 

 these may and doubtless have been transported by man, this cannot apply to the rest, 

 which are insects of weak flight and quite unable to cross large expanses of ocean by 

 their own efforts. It may be urged that these species have radiated from a common 

 centre and that they are still connected by a syngamic chain from South Africa up the 

 east coast, around to India and down through Malaysia to Australia ; but, after all, a 

 chain is no stronger than its weakest link, and I doubt the occurrence of many of these 

 particular species between East Africa and India, although the Distribution-Table will 

 show that some of them occur in Sokotra ; nor can the idea of a syngamic chain be 

 applied to species (such as Amyna octo, Hyblcea piiera, Sylepta derogata, Marasmla 

 trapezalis, and Trichoptilus defectalis) which are found on both sides of the Atlantic. 

 And, unless there is some syngamic connection, it seems incredible that these species 

 should retain the same facies in such diverse habitats, more especially as some of them 

 (e. g. Amyna octo) are extremely variable. It would be a most interesting subject for 

 experiment to see whether specimens of a " species " from South Africa are capable of 

 interbreeding with specimens of the same " species " from the West Indies, Ceylon, and 

 Australia. 



