Resting Attitudes of Lepidoptera. 



By A. E. ToNGE, F.E.S. Read April 22nd, 1909. 



The attitudes assumed by butterflies and moths when at rest 

 afford an exceedingly interesting study and an opportunity for a large 

 amount of conjecture as to the reasons for the wonderful variety of 

 pose adopted by different genera or species. 



Probably the main object attained is the better protection of the 

 insect from its natural enemies, either by mimicry of some inedible 

 object, such as a dead leaf, or by resemblance to its immediate 

 surroundings of so close a nature that the insect is passed by 

 unobserved. But although very many examples of this protection 

 are to be found, some of them positively marvellous in their per- 

 fection, there are so many exceptions that it becomes obvious that 

 other causes are at work to account for them. No doubt one of 

 these is due to the limitations of the human eyesight, resulting in 

 the probability of a large number of well-hidden insects being 

 missed by the searcher, while all, or, at any rate, most of those 

 which are less in harmony with their surroundings, are discovered. 



I had an excellent instance of this on one occasion when photo- 

 graphing a moth on the trunk of a black poplar tree. I daresay 

 that, after finding the insect, I spent fully ten minutes in erecting my 

 camera, focussing, and taking my picture, all the time with my 

 interest centred on the small piece of the tree-trunk on which the 

 moth was sitting ; but it was not until I had finished, and was boxing 

 the moth to take home for a cabinet specimen, that I became aware 

 of a large caterpillar of the red underwing moth, between two and three 

 inches in length, which was sitting exposed upon the bark so near 

 the moth that it had almost been included in my photograph. The 

 caterpillar had fitted itself so marvellously to the rough edges of a 

 ridge of the bark, with which it exactly harmonised in colour, that, 

 although I think I can fairly lay claim to rather more than an 

 ordinary amount of skill in finding insects, as I have collected ever 

 since my schooldays, I had entirely overlooked it. 



This faculty of protection by mimicry and resemblance has no 

 doubt been developed in the course of generations by the law of the 

 survival of the fittest. Like the human hunter, the natural enemies 

 of insects found most of those which were less effectually concealed, 

 and consequently the well-hidden ones carried on the race and 

 transmitted their protective faculty to their progeny, without, of 

 course, any conscious intention, until it became a natural habit. 

 In illustration I may, to take a single species, allude to the marbled 



