Catalogue number: WP1/3/52 Letter from Wallace to fellow insect
collector Henry Walter Bates describing the geographical
distribution of animals and rivers as geographical barriers,
dated December 1861. Wallace writes to Bates, a fellow
entomologist, from Sumatra on his Malay Archipelago expedition.
He congratulates Bates on his 'Papilios' paper (a genus of
swallowtail butterfly) and discusses the need to study nature in
detail to fully understand the geographical limits of certain
species. After his initial praise, Wallace points out some
missed opportunities in Bates' publication. Bates failed to
highlight that rivers 'in a great many cases limit the range of
species or of well marked varieties'. Wallace means the
landscape affects the distribution of species (biogeography). He
cites his own work in the Amazon and Rio Negro, where he noted
that in monkeys 'the species were different on the opposite
banks of the river'. The river acted as a geographical barrier
to their distribution. This made Wallace realis