356 Miscellaneous. 



time. I have noticed that our common meadow-mouse (Arvicola\ 

 which is very dark grey, is scarcely to be seen even in a moonlight 

 night in localities where it is very abundant among grass, and when 

 large numbers are so near that the sound made by their teeth in 

 feeding is very evident. Among insects there are multitudes of 

 instances of colours that are evidently nocturnally protective and 

 which can be explained only on the basis of natural selection, 

 favouring the variations in colour that are in this way most useful. 

 Such colours may or may not be more or less protective in the 

 daytime. Frequently they appear to be just the opposite of pro- 

 tective in the daytime. Thus many butterflies have bright colours 

 that are very conspicuous by daylight and which do not in any way 

 match their customary surroundings. This applies to those species 

 that are black or dark blue, striped or blotched with white, yellow, 

 or orange, and to many species that are spotted or striped with red, 

 orange, and black on the upper surface of the wings, and often also 

 beneath, so that they are conspicuous whether flying or at rest. 

 Their active habits and acute senses probably give them fair pro- 

 tection by day. At night, when resting with the wings folded, the 

 colours of the underside of the wings usually blend very perfectly 

 with those of the flowers on which they roost. Many of our species 

 of Argynnis and allied genera are marked with red, orange, and 

 brown, while there are bright silvery patches on the underside of 

 the wings, which are exposed when at rest. I have observed that 

 these butterflies become very inconspicuous in the moonlight, when 

 sleeping on the goldenrod and other favourite flowers, and that their 

 silvery spots imitate very closely the dew-drops that surround 

 them. 



Numerous nocturnal insects that live on the ground are black or 

 dark brown, which are colours that are protective only at night. 

 This is true of most ground-beetles, many crickets, cockroaches, 

 ants, &c. Many of these insects hide away in the daytime, so that 

 no protective colours are then needed. But many insects that are 

 exposed both during the day and at night have acquired green or 

 yellowish colours that are protective at all times, when living among 

 foliage. Green grasshoppers, katydids, &c. are examples. 



In general, patches, stripes, or spots of strongly contrasted dark 

 and light colours are more likely to be of use by moonlight than by 

 daylight, whether on birds or insects. Reptiles are to a large 

 extent diurnal in their habits and many kinds hide in holes and 

 crevices when at rest, so that our native species of this group 

 appear to afford few good instances of evident nocturnal protective 

 colours, though many may occur when the habits of tropical species 

 become better known. Among nocturnal amphibians protective 

 colours are common, and in many cases they appear to be exclusively 

 for nocturnal protection. Our native nearly black species of 

 salamanders (Amblystoma punctatum and A. opacum) have con- 

 spicuous spots or blotches of white or light yellow. It is evident 

 that these colours have been acquired by natural selection in conse- 

 quence of the nocturnal protection that they afford. Amer. Journ. 

 Sci., February 1897, pp. 132-134. 



