A BRIEF HISTORY
The first clear definition of biological mimicry was that of Henry Walter Bates (1825â92), a British naturalist who spent some 11 years collecting and researching in the Amazonas region of Brazil (Bates 1862, 1864, 1981, G. Woodcock 1969). However, as pointed out by Stearn (1981), Batesâ concept of the evolution of mimicry would quite possibly have gone unnoticed were it not for Darwinâs review of his book in The Natural History Review of 1863. Batesâ observations of remarkable similarity between butterflies belonging to different families led him to ponder what might be the reason for this. He concluded that there must be some advantage, for example, for a âwhite butterflyâ, Dismorphia theucharila (Pieridae), to depart from the typical form and colouration of the family, and instead to resemble unpalatable Heliconius species.1 He also noticed that in all the bright and conspicuous butterfly colour pattern complexes there was at least one species that was distasteful to predators of butterflies (Sheppard 1959). Bates was also ahead of his time in his estimation of the huge and largely undescribed diversity of the Neotropical insect fauna. During his time in Amazonia he estimated that he had collected some 14,712 species, of which approximately 8000 were new, a number that seemed utterly implausible to most entomologists working in the UK at that time (Stearn 1981).
Some groups of insects seem to have an enormous propensity for evolving mimicry, and within apparently closely related groups can have evolved to resemble models of a wide range of colour patterns, shapes and sizes, such as, for example, the dayâflying, chalcosiine zygaenid moths, which are no doubt mostly or entirely MĂźllerian mimics (Yen et al. 2005), or the dayâflying Epicipeiidae moths which, with only 20 or so species, collectively mimic various papillionid, pierid, geometrid, zygaenid and lymantriid butterfly and moth models. No wonder this astonishing potential for variation has fascinated entomologists for years.
A lot of early research involved the collection and publication of field observations and relatively simple experiments, such as feeding various insects to predators and observing reactions (fine examples include G.A.K. Marshall & Poulton 1902, Swynnerton 1915b, R.T. Young 1916, Carpenter 1942). A rather lovely, if quaint, example is that of G.D.H. Carpenter (1921), a medical doctor by profession who was based in Uganda for some time before becoming Hope Professor of Zoology (Entomology) at Oxford University. He describes the results of extensive experiments in which insects were presented to a captive monkey and its responses observed. The article is over 100 pages long and in the foreword he notes that a lot of the observations are tabulated rather than given seriatim because of the âgreat increase in the cost of printingâ. Nevertheless, such observations are essential first steps in understanding whether species are models or mimics or have unsuspected defences.
Around the middle of the nineteenth century, another Englishman, Alfred Russel Wallace (1823â1913), an intrepid traveller, natural historian and thinker, was coming up with important notions concerned with mimicry and aposematism (Wallace 1867). He had earlier travelled to Brazil and collected with Henry Bates and later went on to explore SouthâEast Asia. Indeed, he came up with the idea of evolution by natural selection more or less contemporaneously with Charles Darwin, though unlike Darwin he had little formal education (H.W. Greene & McDiarmid 2005). His early appreciation of the nature of aposematism and thoughts on poisonous snake mimicry are particularly pertinent here.
Mimicry and adaptive colouration have long been popular topics that have grabbed the imagination of both the public and academic biologists due to the incredible detail in many resemblances. Good early treatments include those of Poulton (1890), G.D.H. Carpenter & Ford (1933) and Cott (1940), all of which document numerous natural history observations and interesting ideas. Wolfgang Wicklerâs (1968) popular book on mimicry in plants and animals with many fine illustrations by H. Kacher no doubt fired many people (including myself) with enthusiasm for the topic. KomĂĄrek (2003) provides an excellent and more biographic description of the arguments, ideas and personalities that shaped our understanding of crypsis and mimicry up until 1955 (with some comments on subsequent works up to 1990). Other good general books include Pasteur (1972), D.F. Owen (1980), Forbes (2011) and J. Diamond & Bond (2013), as well as more academic works such as Ruxton et al. (2004a), Stevens & Merilaita (2011) and Stevens (2016). The book by Ruxton et al. provides a critical review of many experiments, models and arguments to do with antiâpredator adaptations in general, not just mimicry and camouflage, but there is a great deal of overlap.
Many arguments, often heated, were also involved in the early discussions of mimicry. Some of the examples show such perfect matching of detail that many scientists found it hard to believe that they could have resulted from natural selection for progressively more similar forms from disparate starting points. Some thought that only major mutations could be involved rather than Darwin...
