Last week, the Natural History Museum in London unveiled a digital archive of the letters of 19th century naturalist Alfred Russel Wallace, the co-discoverer with Charles Darwin, of evolution by natural selection. The archive, introduced on the 100th anniversary of Wallace’s death, naturally focuses on his writings, but also contains some paintings and drawings. Wallace, who spent years in far-flung places collecting specimens, didn’t have the option of pulling out a camera to document his finds. He often sketched or painted his discoveries, including this lovely watercolor of a flying frog which he painted in Sarawak. It may not be Audubon-level in its artistry and detail, but it’s a useful scientific illustration which also has great personality and charm.