How 19th Century specimens solve 21st Century problems

Natural history collections are a treasure trove of data with applications ranging from pest control to insect conservation. This work examines historical specimens of platygastrine wasps (Hymenoptera: Platygastridae: Platygastrinae), parasitoids of gall midges (Diptera: Cecidomyiidae), in order to resolve taxonomic issues and make their data available for research in diverse fields of study. Platygastrinae are considered a “dark taxon”: an abundant and diverse group of insects that are mostly unidentifiable to species due to a lack of diagnostic resources. By characterizing type material and comparing it to modern specimens with molecular data, it is possible to develop diagnostic tools and apply them to contemporary problems. We present a series of interconnected stories demonstrating the importance of historical material: Synopeas rhanis (Walker, 1835) holds the key to identifying a parasitoid of soybean gall midge in Minnesota; Trichacis tristis (Nees, 1834) has a surprising geographical range obscured by 150 years of nomenclatural confusion; and the apparent disappearance of Isocybus grandis (Nees, 1834) may be related to its mysterious ecology. These examples showcase taxonomic detective work that integrates biological data from many different researchers, institutions, and countries over the last two centuries.