Catalogue number: WP1/8/139
Letter from Wallace to Charles Darwin, presenting his arguments against Darwin's views on coloration in female animals, dated September 1868.
Wallace and Darwin regularly corresponded over many years, particularly sharing comments on each other's work. Wallace boldly states 'the more I think of your views as to the colours of females, the more difficulty I find accepting them...'
Looking at the actual letter, we can see lots of inserted words and sentences crossed out. This is a draft version (and unfinished), which gives us clues about Wallace's thought processes when presenting his argument. He summarises the reasons for differences in coloration between some males and females (sexual dimorphism) thus: 'A male, being by structure and habits less exposed to danger and less requiring protection than the female, cannot have more protection given to it by natural selection, but a female must have some extra protection to balance the great danger...'
One example Wallace gives is of female Papilio (swallowtail) butterflies and Diadema butterflies mimicking the inedible Danaida butterflies. He also mentions Henry Walter Bates' 'theory of mimicry', where some butterflies resemble leaves for protection. Wallace made more seminal contributions to the study of the evolution of animal coloration than anyone else.
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View high resolution scans and transcripts of Alfred Russel Wallace's correspondence, including all surviving letters between him and Charles Darwin.