The correspondence between John Gerould and William Hovanitz and the evolution of the Colias hybridization problem (Lepidoptera: Pieridae)

The recently-discovered correspondence between Prof. John Gerould of Darunouth College, who initiated the study of hybridization between synipatric North American species of Colias, and William Hovanitz, who made it the centerpiece of his research program in the 1940s and 50s, sheds light on the sources of Hovanitz's ideas and the evolving interpretadon of that system, which remains a major challenge at the interface of population ecology and population genetics today.