Insects in the Mail, a Quantitative Analysis of Charles Robertson’s Scientific Correspondence

Charles Robertson (1858–1935), a biology professor based in Carlinville, Illinois, conducted a decades-long study recording interactions between species of insects and flowering plants within a 10-mile radius of his home. His records have enduring value as legacy data and provide invaluable insights into an ecosystem that can never be observed firsthand again. However, consistent with the typical scientific practices of his time, Robertson’s publications leave gaps in the information required by scientists reusing his work today. One key source of context for his published findings is his archived correspondence, part of the Charles Robertson Papers at the University of Illinois Archives. His correspondence documents when, where, how, and with whom he exchanged thousands of insect specimens. This paper presents the results of a quantitative analysis of data extracted from Robertson’s correspondence, which provides some of the contextual and methodological information missing from his published works. This analysis demonstrates the essentially collaborative nature of Robertson’s research, the contributions of his collaborators, the challenges of species determination, and the value of considering specimen exchange in analyses of scientific correspondence. The connections documented in this correspondence made his landmark study possible by pooling expertise that was distributed across four decades and throughout the U.S. and Canada. The associated dataset makes that correspondence analyzable and indexes items, correspondents, and specimens to the digitized records, making the original materials more accessible and navigable.