October 2, 1890] 



NA TURE 



557 



Derby, "is interesting, and the success of those who do 



succeed is lasting. What general, what orator, what states- 

 man, what man of letters can hope to leave a memory 

 like that of Darwin? An invalid in health, a man who 

 seldom stirred from home, a man until his later years very 

 little known to the outer world, but who, from his quiet 

 study, revolutionized the thought of Europe, and will be remem- 

 bered as long as Newton and Bacon. If fame be ever worth 

 working for — I do not say it is — that kind of fame is surely, of 

 all, the most durable and the most desirable. Well, I have 

 perhaps digressed from our proper subject, for it is not likely 

 that we have a future Darwin in this room, but it is no 

 exaggeration to say that, as a rule, no man who has taken to 

 science as the work of his life regrets the choice, while men who 

 have done important work in other lines feel like Renan, who, 

 at the height of his literary eminence, tells us in his autobio- 

 graphy that he has often regretted that science, rather than his- 

 torical research, had not been the object of his early pursuit." 



MIMICRY> 



'T'HE relationship of mimicry to other animal colours can only 

 -*■ be explained by giving a short account of the latter. 



I. The commonest use of colour is for concealment {cryptic), 

 enabling an animal (i) to escape its enemies, or (2) to approach 

 its prey. In these (i) protective {procryptic) or (2) aggressive 

 {anticryptic) resemblances, animals seek concealment by a like- 

 ness to some object which is of no interest to enemies or prey 

 respectively. Similar effects may be produced by the use of 

 foreign objects with which the animal covers itself to a greater 

 or lesser extent {allocryptic). 



Examples. — (i) Procryptic Colmirs. A green pipe-fish 

 {Siphonostoma typhle) conspicuous in the water, but well con- 

 cealed among the leaves of Zostera: the brown lappet moth 

 (Gastropacha quercifoUa), conspicuous on a smooth deal board, 

 but well concealed among dead leaves. 



(2) Anticryptic Colours. A large frc^ (Ceratophrys cornuta) 

 from tropical South America, which almost buries itself in a 

 hole in the ground, while the head, which is exposed, har- 

 monizes with the surroundings. In this position it waits till the 

 small animals on which it feeds approach or even walk over it. 



(3) AUocryptic Colours. A small English crab {Steno- 

 rhynchus phalangium) which decks itself with pieces of sea- 

 weed : another small English crab {Hyas coarctatus) was shown 

 with and without its covering of pieces of seaweed (Ulva, Sec). 



Mimicry is closely related to the colours illustrated above, but 

 differs in that the animal resembles an object which positively 

 repels its enemies or positively attracts its prey rather than one 

 which is of no interest to either. It is better, therefore, to defer 

 its consideration until after the description of the colours which 

 form the models for mimicry. 



II. The second great use of colour is to act as a warning or 

 signal {sematic colour), repelling enemies by the indication of 

 some unpleasant or dangerous quality {aposematic or warning 

 colours), or signalling to other individuals of the same species, 

 and thus assisting them to escape from danger {episematic or 

 recognition colours). In a very interesting group of cases {allose- 

 matic), the animal warns off its enemies by associating with 

 itself some other animal with unpleasant qualities and warning 

 colours. 



Examples. — (i) Aposematic Colours. The two unpalatable 

 English moths (Spilosoma urtica and S. mendica, female), when 

 disturbed, assume attitudes which serve to display their con- 

 spicuous yellow and black colours. Portchinski has recently 

 shown that an unpalatable European chrysalis {Limenitis populi) 

 bears the most detailed resemblance to a chrysalis which has 

 been pecked and rejected by a bird. The American skunks 

 (Mephitis mephitica, Conepatus mapurito, &c. ) possess the power 

 of emitting an intolerable stench, and are extremely conspicuous 

 black and white mammals. 



(2) Episcmatic Colours. In the common rabbit the white tail 

 serves as a beacon to other individuals, pointing the way to the 

 burrow. 



(3) Allosematic Colours. A hermit crab (Pagurus bernhardus) 

 is commonly found with a sea anemone {Sagartia parasitica) 

 attached to its shell ; in another hermit crab {Pagurus prideauxii) 



' Abstract of Lectur* delivered by Edward B. Poulton, F.R.S., on 

 Friday, September 5, at the Leeds meeting of the British Association. 



the association is more constant, and the sea anemcne {Adamsia 

 palliata) is specialized for life on the shell of the crustacean. 

 Two crabs {Polydectus cupulifer and Melia tessellata), described 

 by Mbbius in some of the islands round Madagascar, invariably 

 held a sea anemone in each claw. Two other groups of animals, 

 sponges, and ascidians, in addition to sea anemones, are avoided 

 by the enemies of the Crustacea, and these are also made use of 

 by the latter. Thus the hermit crab {Pagurus cuanensis) is 

 found in shells which are covered with a (generally) brightly- 

 coloured sponge (Suderites domtincula) : Mobius also describes- 

 a hermit crab {Ascidiophilus caphyrceformis) which lives in a case 

 formed by an ascidian. 



III. Mimicry may be defined as false warning or signalling 

 colours {pseudosematic), repelling enemies by the deceptive sug- 

 gestion of some unpleasant or dangerous quality {pseudaposematic} 

 or attracting prey by the deceptive appearance of something 

 attractive to them {pseudepisematic). Even foreign objects 

 commonly associated with some well-defended and aggressive 

 species may be mimicked by a comparatively defenceless forn» 

 (pseudallosematic). 



Examples. — (i) Pseudaposematic Colours. The various de- 

 grees of complexity with which protective mimicry occurs in 

 insectswas shown by examples of Indian and African Lepidopterai. 

 {a) Both sexes of the Indian Papilio agestor closely resemble 

 the much commoner and nauseous butterfly Euplcea tytia. 



{b) An Indian moth (Epicopeia philenora) similarly mimics 

 an unpalatable butterfly {Papilio protenor), but in this case the 

 male moth mimics the appearance of the male butterfly, and the 

 female moth that of the female. 



{c) If the mimicking species became common relatively to the 

 mimicked, the deception would be liable to be detected. We 

 therefore find that two or more models are often mimicked by 

 the same species. Thus the male of the Indian Elymnias 

 leucocyma mimics Euplcea binotata, while the female mimics the 

 female of Euplaa linncei. Both these Euplceas are also imper- 

 fectly mimicked by day-flying moths {Amesia midama). So 

 also the male of the Indian Papilio castor mimics Papilio chaon, 

 while the female mimics Euplcea core : in the south, Papilio 

 chaon is absent, and both sexes of the species {Papilio dravid- 

 arum) which represents P. castor, mimic E. core. 



(d) Female butterflies are exposed to more dangers than the 

 swiftly-flying males, and we find many instances in which the 

 former are mimetic, although the latter are not. Thus the 

 female of Hypolimnas bolina mimics Euplcea core, while the 

 male is non-mimetic. The same is true of Hypolimnas misippus, 

 the female of which mimics Danais chrysippus. Two forms 

 closely allied to the latter (some regard them as merely varieties) 

 are also mimicked by the former. 



{e) The mimetic females also often resemble two or more dif- 

 ferent species of nauseous butterflies. Thus the female of Papilio 

 pammon appears in two forms, mimicking respectively Papilio 

 hector SLnd P. aristoloche ; while ihe iemaXts, oi EuHpus halitherses 

 (the male of which is probably mimetic) mimic Euplcea rhadam- 

 anthus and Euploea deione. 



(/) There are also striking examples in which the non- 

 mimetic ancestor of a mimetic species has been preserved, e.g, 

 in an adjacent island. Thus the female of Elymnias undulariy 

 mimics Danais genutia in Sikkim and North-East India ; in 

 Rangoon and Burmah there is a variety of the latter with white 

 hind wings which is as common as the typical form, and the 

 female of E. undularis is beginning to mimic "this variety ; in 

 South India E. undularis is represented by E. caudata, in 

 which the male is also beginning to mimic D. genutia, and the 

 female is a more perfect mimic than in the other localities ; in. 

 the Andaman Islands E. cottonis represents E. undularis, and' 

 both sexes appear to be non-mimetic, while D. genutia has never 

 been recorded from this locality. A still more wonderful ex- 

 ample is found in Africa and adjacent islands. Papilio meriones 

 of Madagascar is non-mimetic, and the sexes are alike ; the 

 same is true of a closely-allied species, P. humbloti, recently 

 discovered in Grand Comoro, and of P. antinorii recently found 

 in Abyssinia. A very nearly related species in West Africa has 

 a closely similar non-mimetic male, while two forms of female 

 mimic Danais chrysippus and Danais niavius. In South Africa 

 Papilio cenea has an almost identical male, while the female^ 

 mimic D. chrysippus, the southern form of D. niavius, and two 

 varieties of D. echeria. 



{g) There are also examples which show us the origin of 

 mimicry, in which the resemblance is very imperfect, but, never- 

 theless, sufficient to afford protection. The blue Euplceas of 



NO. TO92, VOL. 42] 



