In his work with the Amazonian butterfly, he described what came to be known as “Batesian mimicry” – a form of mimicry in which a harmless species has evolved to imitate the warning signals of a harmful species directed at a common predator (in a paper read before the Linnaean Society in 1861). His book, The Naturalist on the Amazons (1863), brought him fame and praise from Darwin. He was assistant secretary of the Royal Geographical Society for 27 years, until his death in 1892. Although not explicit in his own works, and described elsewhere as a Unitarian, that Bates was an outspoken agnostic is recorded in Edward Clodd’s Memoir (1916).