THE VALUE OP PROTECTIVE RESEMBLANCE IN MOTHS. 263 



N, Manders. The questions specially discussed by the writer were 

 how far moths are liable to the attacks of birds ; and whether, if such 

 attacks produce a serious struggle for existence, the value to the moth 

 of protective resemblance is such as to account, through natural 

 selection, for such changes of pattern or colour as may have produced, 

 in the course of generations, a harmonisation of the moth to its 

 normal surroundings. 



Now I think there cannot be the smallest doubt that many 

 species of birds do prey upon both moths and butterflies. The fact 

 must surely be sufficiently familiar to the most casual student of 

 nature. I have repeatedly seen Sparrows chase and capture the 

 " Whites," and Swallows stoop at the same butterflies, and also at 

 Goneptertjx rhanini. Only this summer I watched three Swallows, one 

 after the other, capture and drop again a specimen of Spilosoma 

 Inhricipcda, which I had disturbed during the daytime. Ultimately it 

 made its escape into some ivy, and I concluded that either it was too 

 large for the bird's gape, or else distasteful to their palate for some 

 reason. Nightjars and Flycatchers catch moths by night and day 

 respectively, and I have found the wings of butterflies in the castings 

 of Kestrels, and of moths in those of Owls. Similar instances might 

 be multiplied ad infimtitin. 



But all this, though without doubt it has its bearing on the problem 

 of mimicry, has none at all on that of protective resemblance. To 

 have any Ijearing on the latter it must be shown that birds and reptiles 

 capture moths or butterflies at rest, and not during flight. To quote 

 Lieut. -Col. Manders, " The capture of an odd specimen here and there 

 by a sparrow or other bird, though a matter of almost daily observation 

 during the summer months, can have little or no effect on the general 

 moth population, and certainly none in the production of a protective 

 colouring by means of natural selection. What is required is a hunt 

 for some bird or birds which make moths a speciality in their dietary, 

 and which show under natural conditions a marked preference for 

 certain species." I am not quite sure that too much importance ought 

 to be attached to the last condition, as when one considers the large 

 number of insectivorous birds, and the enormous quantities of insects 

 each pair brings to its nestlings during the breeding season, one can 

 easily believe that the fact that any of them preyed habitually on 

 moths at rest might tend, in the course of ages, to promote, by natural 

 selection, protective resemblance in several different species. 



Now it is my firm conviction that some birds do prey on moths 

 and butterflies, even when at rest. 1 have frequently seen and 

 captured both moths and butterflies with a clean-cut, triangular 

 fissure in one or more of the wings, quite dift'erent from the irregular 

 frayed tearing which is produced by contact with brambles or thistles 

 in windy weather ; and I have always been inclined to attribute such 

 gaps in their wings to their having been seized by birds, and having 

 made good their escape with the loss of that portion of the wing 

 actually laid hold of by the beaks of their would-be devourers. So 

 far, of course, there is nothing to show whether the injury was 

 inflicted upon the insects when in flight, or at rest. But I have also 

 frequently come across cases in butterflies, and among the Geometers, 

 where gaps exactly corresponding both in size, shape, and position, 

 existed in the wings on both sides. Now assuming the injuries to 



