Kane — On Iri^h Lepkloptera. 105 



XII. — Repoet on Ieish Lepidopteea. By W. F. DeY. Kaxe, M.A. 



[Eead, January 28, 1884.] 



3Iy researclies this summer, chiefly on the south and south-Tvestern 

 coast of Ireland, have been attended Tvith some very interesting results 

 in regard to the distribution of species, and may, perhaps, help to 

 elucidate in a small degree the problem as to whence this island 

 originally derived its Lepidoptera. 



The migration of this order of insects has not yet been studied as 

 the subject deserves, considering the light it is capable of throvring 

 on the early history of islands and portions of continents, in conjunc- 

 tion with botany and geology. 



Hr. ^"allace has recorded some remarkable facts observed during 

 his travels in the Malay Archipelago, and some of his conclusions 

 bear upon the subject to which I invite your attention. 



The introduction of members of the tribe of Lepidoptera into such 

 an island as this, may be presumed to have taken place in any one of 

 the following ways : — 



Fii'stly (if our geological history permit the supposition), by over- 

 land migration, previous to our disruption from the mainland. 



Secondly, by flight, either voluntarily in favoui-able weather, or 

 by a fertile female being blown across the sea by a storm. 



Thirdly, by water — ships frec^uently harboiu-ing insects which have 

 flown on board, and lodged in the folds of sails or other gear, or 

 else by the importation of their ova on some living plant or dried 

 herbage. 



I will offer a few remarks on each of these three possible hypo- 

 theses. 



Those who have not studied the subject will most likely jump to 

 the conclusion that most of our moths and butterflies came hither by 

 flight. l!^ow, 3ili'. Wallace states that an arm of the sea of far less 

 width than that which separates the Isle of ITan from the neighbour- 

 ing coasts has in many instances in the Malay Archipelago proved an 

 insuperable barrier to a large number of species, even of birds of 

 ordinary powers of flight. He says: — "It may perhaps be thought 

 that birds, which possess the power of flight in so pre-eminent a 

 degree, would not be limited in their range by arms of the sea, and 

 would thus afford few indications of the former union or separation 

 of the islands they inhabit. This, however, is not the case. A very 

 large number of birds appear to be as strictly limited by watery bar- 

 riers as are quadrupeds." Again — "Insects fui'nish us with similar 

 facts wherever sufiicient data are to be had." In another place Mr. 

 Wallace poiuts out that, although the strait between Eali and Lom- 

 bock is only fifteen miles wide, yet that the characters of the natural 



