BUTTERFLIES AND MOTHS IN AUTUMN 59 



hand, seem to have a distinct though partial sense which 

 leads them when flying about by day to settle on yellow 

 flowers and dead leaves, chips of yellow wood, and other 

 objects which help to conceal them. They do not always 

 do this ; they will feed in spring, for example, on purple 

 vetch, and on dahlias of many colours in the autumn garden. 

 But the habit is sufficiently marked to be interesting and 

 significant. Sometimes they seem to hibernate in thick 

 heather, from which they may sometimes be disturbed in 

 October and November ; and among the dark-brown heather- 

 twigs their greenish-yellow under sides cannot help to conceal 

 them, unless, as is possible, they serve to imitate a yellow 

 leaf of sorrel, or sallow, or some other heath-growing plant. 

 But they have lately been found hibernating in quite a 

 different situation among growing ivy leaves in a hedge ; 

 and there their hooked greenish-yellow wings gave a striking 

 imitation of the under sides of the pointed ivy leaves. The 

 small pale spot in the centre of the wing precisely imitated 

 a fleck of decay on the leaf. The two species of clouded 

 yellows have a similar spot ; and although their special place 

 of hibernation is not known, it is highly probable that they 

 hide in some spot where they imitate pale yellow leaves. 



Clouded yellows are as erratic in their appearance as 

 painted ladies, and for the same reason. Our British supply 

 is periodically reinforced by immigrants from the opposite 

 shores of the Channel ; and the number of their descendants 

 depends on the weather for the next year or two. There 

 are two species, the pale clouded yellow being much scarcer 

 than the common one. They are most plentiful in Kent, 

 where the migrants from France most thickly settle ; but in 

 some years they are fairly general in the south of England 

 in late summer and early autumn. The common species is 

 of a deep saffron tinge, a good deal richer than the colour 



