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 realise anyone collecting on the banks of large rivers should note 'from which side every specimen came'. It was only through experience that Wallace saw the importance of such detail.
Wallace suggested a few geological reasons for the presence of different species on opposite river banks. He then laments his current lack of insect collecting, mainly due to poor weather. 'I am getting however some sweet little Lycaenidae [a type of butterfly],' he admits, 'which is the only thing that keeps me in good spirits.' Wallace had such a passion for his work that even the smallest success could keep him happy in the worst circumstances.
For enquiries about the Wallace Collection please email the library
View high resolution scans and transcripts of Alfred Russel Wallace's correspondence, including all surviving letters between him and Charles Darwin.