110 Proreedings of ihe lioyal IrUJt Academy. 



once prevailed even in Kerry, whose fiords, -with moraines and glacier- 

 planed rocks, bear a like testimony. 



But unless Scotland subsequently, yet before its separation from 

 Ireland, enjoyed a very much warmer climate than at present, of 

 which I believe there are no tokens, the heat-loving species, such as 

 Deiopeia pulchella, Deilephila celerio, D. livornica, Lithosia caniola, 

 and Heliothis peltiger, could not have entered by so northern a route. 

 Of this last insect, new to Ireland, I took specimens this summer 

 at Castlehaven and Crookhaven. It is distinctly confined in its range 

 to the south of Europe, Yienna being its extreme northern limit ; is not 

 found in Belgium, but occurs in some spots in the south coast of 

 England. 



We are thus reminded of the existence of certain Spanish flora in 

 the south and west of Ireland, which would suggest that the sound- 

 ings between that coast and Brittany may possibly indicate a former 

 connexion with the Continent. But I do not know that there is evi- 

 dence enough forthcoming to lift the theory out of the region of bare 

 speculation. 



I have now discussed shortly two of the three hypotheses, the 

 facts in regard to which seem to point that the greater portion by far 

 of our Lepidopterous fauna must have entered overland, though the 

 presence of south Europsean species offers a difficult problem for solu- 

 tion. And, before passing on, I would like to call attention to what 

 seems to me a very probable and curious illustration of the theory of 

 " survival of the fittest," in conformity to peculiar conditions of life. 

 I find that all except two of the thirteen British moths which, like N. 

 zonaria, have apterous females, although belonging to different genera, 

 have this in common, namely, that their period of emergence and 

 breeding is from October to March inclusive, when high winds pre- 

 vail ; and that they are all tree-feeders, or in the case of N. zonaria, 

 live on the scanty herbage of bare and exposed shores. Being insects 

 of weak flight, the possession of wings by their females would con- 

 stantly expose them to be blown from their food-plant, so that their 

 larvae, when hatched, would perish. If this malformation was inde- 

 pendent of their breeding habits, it would scarcely, one would think, 

 be confined to the female sex ; and if it were a purely generic charac- 

 teristic, one would expect those species also which have a summer 

 emergence to partake equally of this peculiarity. 



However there are two exceptions in the genus Orgyia, namely, 

 the closely-allied forms of 0. antiqua and 0. gonostigma. The former, 

 however, seems to have adopted very unsettled habits, being poly- 

 phagous, and breeding irregularly throughout the summer, from June 

 to the end of October. I therefore consider it, and possibly its relative, 

 0. gonostigma, to have anciently had an October emergence, but sub- 

 sequently to have adapted itself to changed conditions of climate and 

 food. The occiuTcnce of this deprivation among other orders of in- 

 sects, too, throws a convergent light upon the subject. 



