BATES, HENRY WALTER (1825-1892), English natural ist and explorer, was born in Leicester. In 1844 he met a congenial spirit in Alfred Russel Wallace, and in April 1848 the two friends sailed in a trader for Para. They had little or no money, but hoped to meet their expenses by the sale of duplicate specimens. After two years Bates and Wallace agreed to collect independ ently, Wallace taking the Rio Negro and the upper waters of the Orinoco, while Bates continued his route up the great river f or 1,400m. He remained in the country 11 years, during which time he collected no fewer than 8,000 species of insects new to science. His long residence in the tropics with the privations which it entailed, undermined his health. Nor had the exile from home the compensation of freeing him from financial cares, which hung heavy on him till he had the good fortune to be appointed in 1864 assistant secretary of the Royal Geographical Society, a post which he retained till his death. Bates is best known as the author of one of the most delightful books of travel in the English language, The Naturalist on the Amazons (1863), the writing of which, as the correspondence between the two has shewn, was due to Charles Darwin's persistent urgency. "Bates," wrote Darwin to Sir Charles Lyell, "is second only to Humboldt in describing a tropical forest." His most memorable contribution to biological science was his paper on the "Insect Fauna of the Amazon Valley," read before the Linnaean Society in 1861, in which he clearly stated and solved the problem of "mimicry," or the superficial resem blances between totally different species and the likeness between an animal and its surroundings, whereby it evades its foes or conceals itself from its prey. A man of varied tastes, he devoted the larger part of his leisure to entomology, notably to the classifi cation of coleoptera. Of these he left an extensive and unique collection, which, fortunately for science, was purchased intact by Rene Oberthur of Rennes.