An extensive literature on the history of entomology (see Literature Guide below) provides the basis for a discussion of aspects of ecologically relevant entomology for the 1800s, with two topics deferred to later parts of this history: diseases of insects and insects as vectors of human disease, to part 46 on parasitism and the germ theory of disease; and pollination ecology and domestic bees, to part 52 on symbiosis. We saw in parts 21 and 30 (Egerton 2006, 2008) that there were many important studies on insects during the 1700s, and in parts 33 and 41 (Egerton 2009b, 2012a) we met notable entomologists of the 1800s: Thomas Say (1787–1834) and Henry Walter Bates (1825–1892). Alfred Russel Wallace (1823–1913), discussed in parts 41–42 (Egerton 2012a, b), also notably contributed to entomology. Charles Darwin (1809–1882) had collected beetles at Cambridge and insects on the voyage of the Beagle; he discussed insects in the Origin of Species, and he studied insects in relation to pollination and insectivorous plants (Riley 1882, Egerton 2010, 2011b, Carton 2011). Some of these men might themselves be classified as “stamp collectors,” but taxonomy and systematics were especially important for entomology if it were ever to become a sophisticated science, because it was essential for zoologists to distinguish whatever species they studied so others could verify or refute claims made about particular species.