THE THEORY OF MIMICRY 139 



terned animals as the zebra and giraffe, tor instance, de 

 facto is not protective under the usual conditions of their 

 environments; and, further, that as the carnivora hunt 

 almost exclusively at night and by scerit^ the coloration, 

 be it what it may, is of little account. 



The brothers Thayer, American artists and authors, 

 in a work entitled '' Concealing Coloration in the Animal 

 Kingdom,'- give many expensive plates to illustrate how 

 conspicuous colours and patterns lend themselves to con- 

 cealment under certain environmental conditions, which, 

 however, are evidently not always natural conditions ! 



For the same reasons, Capt. Selous doubts the efficacy, 

 for protective purposes, of the snowy garb of most of the 

 arctic animals, or the assimilative colours of desert ani- 

 mals. He considers that these assimilative colours must 

 be due to the influence (physical) of their environment, 

 and that natural selection has no say in the matter. 

 Mutual recognition marks are equally condemned, and, 

 I think, quite rightly, for the senses other than those of 

 sight are quite ignored. However, as regards the cryptic 

 coloration of desert and arctic animals, Capt. Selous 

 overlooks the possible constitutional benefits that may 

 accrue to them by their coloration, which may make these 

 cases accountable to natural selection. 



I cannot recall a single example among the insects, at 

 any rate, in which purely pro-cryptic disguise may not 

 be of service either for protection, aggression or both, 

 provided it is conceded that the faculties employed are 

 those of visibility alone. There are, however, innumer- 

 able cases of resemblance between organisms to which I 

 can assign no use, so far as my knowledge goes, and 

 among the most remarkable that I can recall, is the mar- 

 vellous simulation of a small grass-snail by the bag- worm 

 larva of a Psychid moth, Apterona species. Dr. D. Sharp, 

 in " Cambridge Natural History — Insects," Part II, page 

 394, refers to it as follows: — '^The most extraordinary 

 are some of the genus Apterona, which perfectly resemble 

 the shells of Molluscs such as snails; indeed the speci- 



