MIMICRY 



207 



close superficial resemblance to each other has 

 been known for a lon period of time. The names 

 given to various species of British moths are suffi- 

 cient proofs of this. Sucli names as Bombyli- 

 formis, Apiformis, Bembeciformis, &c. imply a 

 recognition of the resemblance between these 

 species and others belonging to an entirely differ- 

 ent order. The meaning of such likenesses was, 

 however, unknown until the appearance of H. 

 \V. Bates's classical paper in 1802. In this essay 

 the author shows that the species which lias departed 

 from the normal type of its group (the mimicker) is 

 far rarer than the form which it resembles, while 

 the latter (the mimicked) is abundant and well 

 defended by some special protection, such as the 

 II-I--I--MIHI of an unpleasant taste or smell or the 

 power of stinging. Bates's observations were con- 

 ducted in tropical America, where abundant, con- 

 spicuous, slow-Hying, nauseous butterflies ( Heli- 

 conid.-e and Danaiiue) are closely mimicked by 



he family containing our common garden 

 white butterflies ) and other butterflies, and in many 

 c-:isc> by day-Hying moths. Subsequent observation 

 has confirmed liates's suggestion. Wallace found 

 numerous instances of mimicry among the Lepi- 

 doptera of India and the Malay Archipelago, 

 and Trimen directed attention to similar facts 

 among South African butterflies. The latter 

 include the most remarkable instance of mimicry 

 yet discovered. The male of a South African 



swallow tailed butterfly (I'upilin ccnca) is typical 

 in appearance and possesses the characteristic 'tails' 

 on tne hind-wings : the female is utterly unlike the 



male in the colouring and form of. the wings, the 

 ' taiU ' leing entirely alisent. While the female is 

 so different from the male of its own species it 

 appears in three well-marked varieties mimicking 

 three different species of the nauseous genus Danais 

 viz. the black brown-spotted D. Echcria, the 



black and white D. niaviux, and the black reddish- 

 lirown and white D. chrysi/ipns (see fig. 2/V). 

 In West Africa a closely related swallow-tail 

 (P. merope) has a very similar male, and females 

 mimicking I>. eArynpoto and the West African form 

 of I), niaviui. VVliile such remarkable changes 

 have occurred on the mainland of Africa, the an 

 central form from which these mimetic species have 

 lii'i'M developed has lieen preserved comparatively 

 unchanged in the inland of Madagascar, as the 

 closely related Papilio meriunet in which the 

 female much resembles the male and is non-mimetic. 

 Similar sperie* with sexes almost alike have been 

 found in the Comoro Islands (P. IntnMoti) and in 



Abyssinia (P. antinorii). This example strongly 

 enforces a conclusion also arrived at by Bates and 

 Wallace viz. that the females are far more fre- 

 quently mimetic than the males. Wallace has 

 explained this because of the especial dangers 

 incurred by the female during her slow flight when 

 laden with eggs, and her exposure to attack during 

 oviposition. 



The examples selected for illustration were 

 lent by Colonel Swinhoe ; the figures are about 

 half the natural size. Fig. 1 represents the male 

 of the Indian and African Hypolimncu misippvs : 

 it is non-mimetic and very unlike the female, 

 being distinctly marked with a large iridescent 

 blue spot on each of the four wings. The 

 iridescent spots on the right wings appear to 

 be larger than those on the left, l>ecause they 

 are seen at a different angle. The male remains 

 unchanged in the localities where its female alters 

 in correspondence with the form it mimics. 

 Fig. 2 is the commonest form of female, which 

 mimics the above-mentioned Danaw clirysippits 

 (fig. 2A), occurring nearly all over the Old World. 

 In Aden and some parts of Africa the latter butter- 

 fly is represented by a variety or sub-species with 

 white hind-wings (Danais alcippus); see fig. 3A. 

 In the same localities there is a similar variety of 

 the female Hypolimnas (the alcippoiiies form), 

 shown in fig. 3. Finally, in Aden and certain 

 African localities there is another variety or sub- 

 species of the Danais ( D. tloriypvs ) without the 

 black and white marks at the tip of the fore-wing, 

 shown in fig. 4A ; while the Hypolimnas follows 

 with a similar form of female, seen in fig. 4. This 

 latter is also common in the south-west of India, 

 where it has been stated that the mimicked form 

 (D. doripptu) does not occur. Colonel Swinhoe, 

 however, felt sure that the existence of the 

 miniicker implied the former presence of the 

 mimicked species. He tested this hypothesis by 

 examining large nuiuliers of the Danais, and he 

 found that the ilorippus form does exist in that 

 part of India, although it is extremely rare : he 

 came across about a dozen in four or five years. 

 It is prol>able that dorippus has been nearly sup- 

 planted by the dominant form c/trysippits, the 

 resemblance between the two being sufficiently 

 close for the mimic of the former to be mistaken 

 for the latter. The case forms a most interesting 

 exception to Wallace's third law quoted below. 



The butterflies which afford models for mimicry 

 chiefly belong to the two families Danaidte (includ- 

 ing Eupluca, Danais, and Hestia) ami Acra>idae, in 

 addition to the Heliconidie of tropical America. 

 There is some direct and much indirect evidence to 

 show that all mimicked species are specially pro- 

 tected by an unpleasant taste or smell. Wallace 

 has concisely stated the conditions under which 

 mimicry occurs, as follows : ' ( 1 ) That the imitative 

 species occur in the same area and occupy the same 

 station as the imitated. (2) That the imitators 

 are always the more defenceless. (3) That the 

 imitators are always less numerous in individuals. 

 (4) That the imitators differ from the bulk of their 

 allies. (5) That the imitation, however minute, is 

 external and visible only, never extending to internal 

 characters or to such as do not affect the external 

 appearance. ' 



Examples of mimicry are also well known in 

 other orders of insects. The formidable Hymen- 

 optera (including the hornets, wasps, bees, and 

 ants) are frequently resembled by defenceless 

 insects belonging to other orders, such as moths 

 (Lepidoptera), beetles (Coleoptera), flies (Diptera), 

 &c. The most remarkable example yet described 

 was discovered by W. L. Sclater in tropical America. 

 The leaf-cutting ants (CEcodoma) are extremely 

 abundant in this part of the world, and present a 



