These data sets provide results of no-choice laboratory experiments on host specificity of 13 populations in seven species from three species complexes in the genus Aphelinus (Hymenoptera: Aphelinidae). They also provide results of experiments on the mechanisms of host specificity in three parasitoid species with narrow host ranges.

*Aphelinus glycinis* was collected in the Peoples Republic of China under a Memorandum of Understanding between their Ministry of Agriculture and the United States Department of Agriculture (USDA). *Aphelinus atriplicis* was collected by employees of the USDA, Agricultural Research Service (ARS), in the Republic of Georgia with the permission of that government. The parasitoids were imported into the USDA, ARS, Beneficial Insect Introductions Research Unit containment facility in Newark, Delaware, under permits from the USDA, Animal and Plant Health Inspection Service (Permit Numbers P526P-08-02142 and P526P-09-01929). No specific permissions were required to collect *Aphis craccivora* or *Acyrthosiphon pisum* because these are cosmopolitan aphids that occur in the field throughout North America. None of the species collected or studied are endangered or protected.

The Sustainable Corn CAP (Cropping Systems Coordinated Agricultural Project: Climate Change, Mitigation, and Adaptation in Corn-based Cropping Systems) was a multi-state transdisciplinary project supported by the USDA National Institute of Food and Agriculture (Award No. 2011-68002-30190). Research experiments were located through the U.S. Corn Belt and examined farm-level adaptation practices for corn-based cropping systems to current and predicted impacts of climate change.