A nice little article about Wallace's frog in the current edition of the Scientist.
Wallace painted this watercolor of Rhacophorus nigropalmatus in 1855. A newly discovered species, the frog was found in a part of Borneo’s rainforest that echoed with the sounds of workers felling trees and transporting coal. The disturbance brought a diverse range of creatures out of hiding and, in the case of the frog, into the scientific record books.
He later discussed the species, named Rhacophorus nigropalmatus or “Wallace’s frog,” as an example of evolution’s stepwise process in his 1869 book The Malay Archipelago, in which he included a woodcut based on his original frog painting: “[I]t is very interesting to Darwinians as showing that the variability of the toes which have been already modified for purposes of swimming and adhesive climbing, have been taken advantage of to enable an allied species to pass through the air like the flying lizard.”