Page:The Zoologist, 4th series, vol 1 (1897).djvu/114

88 End. Strange to say, there were still a few nesting in Gray's Inn Square. — (64, Hereford Road, Bayswater).

The Stock-Dove in Ireland.—I shot a Stock-Dove here on Jan. 6th. It is a level wooded locality about twenty miles from Ravensdale, where Lord Clermont recorded the first Stock-Dove in Ireland (Zool. 1876, p. 4798). I have shot many hundreds of Ring-Doves here, but have never secured a Stock-Dove before.— (Black Hall, Drogheda).

A Proposed Explanation as to the Appearance of Light- and Dark-coloured Butterflies during the Day.—Dr. Gregory, in his 'Great Rift Valley' (pp. 275–6), has made some original suggestions on the colours of butterflies as observed by him in East-Central Africa. He writes as follows:—"Another point which interested me in reference to insect coloration was the influence of the different capacities for the absorption of heat possessed by different colours. A black object becomes more heated than a white one, when both are exposed under the same conditions. An insect has so much surface in proportion to its bulk that dark-coloured species are heavily handicapped when exposed to the intense sun of the tropics. This is the simple explanation of the fact, which impressed itself upon me as soon as I began to collect butterflies, that the light-coloured species fly in the daytime, and the dark ones in early morning and at dusk. I made considerable collections at Ngatana, at all hours of the day, to test this point. Thus on Jan. 30th I began collecting at 5.45 a.m., and found only species which are mainly of dark brown colour, such as Hypolimnas misippus and Junonia clelia. At 6.30 a reddish-brown species, Limnas klugi, began to appear, and this was the only species caught during the next half-hour, though this was abundant. A little before half-past seven a light brown species, Acræa cæcilia, made their appearance, followed immediately by numbers of light-coloured butterflies, such as Teracolus syrtinus, which is all white except for a red tip to the wings, and Catopsilia pyrene, which is wholly of a light creamy white. The dark brown forms disappeared from the open steppes before seven, and they were followed into obscurity by the light brown Limnas, of which not a single specimen could be found during the heat of the day. Then the open 'barra' was tenanted only by white and light coloured species. This rule, however, is not universal, for other factors modify it. Thus in dull cloudy weather the dark-coloured forms fly abroad all day, while some species of rapid flight habitually do so, such as many of the swallow-tail butterflies. Papilio demoleus, for example, a common species in the Sabaki and Tana valleys, was met with at all times of day; but it lived mainly under trees, darting out across open places from one shady place to another."