PROTECTIVE RESEMBLANCE. . 165 



dris diihjuiata, it would appear also that, notwithstanding the fact of 

 their colours matching their surroundings so well, the resemblance 

 was not "protective" as they were so easily found. It is not certain, 

 however, that the M. diili/iiiata were taken at rest, as Mr. Stiff says 

 " they generally drop when disturbed," as they would be by a search- 

 ing bird, and movement would be fatal. 



With regard to the large brown lizards and the blue-bottle fly, I 

 imagine that the green and grey, and the vivid green lizards would 

 have been equally successful in the same situation, provided they kept 

 motionless. 



With regard to the clean cut gaps often found in the same position 

 in the wing on both sides of butterflies, Mr. W. J. Kaye, in his Presi- 

 dential Address to the South London Natural History Society, on 

 January 25th, 1912, says, "specimens with a single notch, that is only 

 one wing notched, are no proof that the injury was not self-inflicted, 

 by the insect flying through rough scrub or what not. But specimens 

 with notches in both forewings or both hindwings, which coincide 

 when the wings are folded, cannot be a self-inflicted injury, as it must 

 have been done while the insect was settled." I think nobod}^ can 

 doubt this. 



I imagine, however, that if a bird seized a butterfly at rest it would 

 have little chance of getting away, and if it did the result would be a 

 rough tear. Unfortunately few collectors think of keeping chipped 

 specimens, especially if they are common species, and I am afraid I 

 must also plead guilty, but have often released specimens with pieces 

 of the wing membrane hanging. Colias cdiisa $ s, however, are not 

 so readily released, and I have in my collection a specimen with a 

 notch in the same position in both hindwings, on one wing, however, 

 the piece of wing membrane is still hanging. Now I submit that this 

 could not be the work of a bird or other enemy, otherwise both pieces 

 would have been taken. What I suggest is that the sharp edge of a 

 grass blade, or something similar, in windy weather makes an incision 

 in the wings. When the insect flies the pieces of membrane flap back- 

 ward and forward and are eventually severed. 



The Rev. G. Wheeler {J'}nt. llecord, vol. xxv., p. 190) says, "It is 

 well known that the darkest forms of many grey moths of widely 

 different genera are now by far the commonest in and around London, 

 and that the area in which this takes place is enlarging itself almost 

 annually. Is it seriously contended that this is to be accounted for as 

 might seem on the surface to be the case, by Miillerian mimicry, 

 instead of being one of tlie tiiu.st obvious and easily understood instances of 

 the irorkini/ of natural selection by means of protective resemblance ' " 



Mr. Wheeler does not say what is the agency that does the selecting, 

 but I presume he has in mind the attacks by birds. He does not 

 mention any species in particular, but I have in mind one or two 

 species — I'riaeiia /^s/, Apatela aceris, and Hemerophila abruptaria, all 

 of which I have had under observation for some years in East Dulwich. 

 All the specimens of A. psi are melanic, and rest on dark lime trunks 

 and yellow brick walls. On the former they are quite easily seen, but 

 on the latter are most difficult to detect, owing to the chequered surface 

 of the bricks. If this melanism is brought about by " protective " 

 resemblance as he suggests, how is it that A. aceris keeps its pale grey 

 colour notwithstanding that it rests in the same situations ? 



