‘Among oak trees swelling with galls’. Visualizing Plant-Insect Interactions in Botanical Illustration and Natural History Collections

Galls—plant outgrowths induced by organisms such as insects, mites, and fungi—have long attracted the attention of naturalists due to their remarkable morphological diversity and hidden complexity. As products of interspecific interaction, they constitute a privileged object for examining how relationships between organisms have been conceptualised and visually represented from the early modern period to the twentieth century. This contribution examines the history of gall illustration by treating images (printed illustrations, drawings, and photographs) as primary sources for the study of scientific practice. It focuses on the ways in which visual representations have variously documented, selected, and rendered visible different components of the phenomenon—host plant, gall structure, and inducing organism—while often fragmenting or obscuring the ecological interactions that produce them. Drawing on archival materials from the collections of the botanist Alessandro Trotter (1874–1967), held at the Botanical Museum of the University of Padua, this article reflects on the shifting visual and epistemic frameworks through which galls have been represented in scientific practice and communication.