28 THE WONDER OF LIFE 



A general resemblance to surroundings is often life- 

 saving, and one must not be in haste to exclude the possi- 

 bility that some animals actively seek out the surroundings 

 with which they best harmonize. With certain backgrounds 

 a woodcock or a curlew upon its nest fades into its sur- 

 roundings and becomes practically invisible, just as does 

 the brown lizard on the sand, the green snake among the 

 branches, the transparent arrowworm in the sea, the 

 mountain hare among the snow, the hare on the ploughed 

 land, and one might fill a page with good examples. 



It has been noticed that a grey donkey in a field at night 

 may be quite invisible at a distance of a few yards, though 

 the noise of its cropping is very distinct. On a night with 

 diffused ground light, when cows were visible at a distance 

 of eighty yards, a donkey was quite invisibla at eight. It 

 is probable that his lighter under-surface served to diffuse 

 what light there was. A careful observer writes : 



' On his starboard quarter at four yards distance, his dark 

 head appeared as a moving blur, but " stern on " at that 

 distance he was completely invisible an " airy nothing " 

 though, like Polonius, " at supper ". It was most extra- 

 ordinary to hear the animal feeding and to be unable to see 

 a vestige of him.' 



There is an interesting moth, the Golden-Eight moth 

 (Plusia nwneta), which during the last half-century has been 

 spreading westward and southward from its Russian head- 

 quarters. Its first appearance in Britain was in 1857 ; a 

 great invasion occurred in 1890 ; since then it has diffused 

 itself over England. It is called ' Golden Eight ' because 

 of the markings on its golden-grey wings. When it is at 

 rest, however, it puts on the mantle of invisibility and 



