The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is native to Asia where it is an occasional pest of soybean, Glycine max (L.). Aphis glycines was found during 2000 in North America and since then has spread throughout much of the area where soybean is grown. In Asia, A. glycines seldom reaches damaging levels; however in North America, it has become the most important insect pest of soybean, decreasing yields and incurring large control costs. Field surveys and exclosure experiments in China showed that natural enemies can limit soybean aphid abundance. A project to find, evaluate, and introduce Asian natural enemies into North America was initiated in 2001, with an emphasis on parasitoids. To ensure that introductions of exotic parasitoids would have minimum impact on non-target species, we tested host specificity of all candidates for introduction. 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. See the included README file list for more details on methods and citations for these data files. Resources in this dataset:Resource Title: Data dictionary for data from: Host specificity of Aphelinus species collected from soybean aphid in Asia. File Name: data_dictionary_host_specificity_of_Aphelinus.csvResource Title: Collection information for Aphelinus species from soybean aphid for: Host specificity of Aphelinus species collected from soybean aphid in Asia. File Name: Aphelinus_soybean_aphid_culture_data.csvResource Title: Parasitism of aphid species by Aphelinus species collected from soybean aphid. File Name: Aphelinus_soybean_aphid_host_use.csvResource Title: Parasitism of Aphis species by Aphelinus coreae. File Name: Aphelinus_coreae_with_Aphis_species.csvResource Title: Parasitism of Aphis species by Aphelinus glycinis. File Name: Aphelinus_glycinis_with_Aphis_species.csvResource Title: Parasitism of Aphis species by Aphelinus rhamni. File Name: Aphelinus_rhamni_with_Aphis_species.csvResource Title: Summary behavior of Aphelinus coreae exposed to various aphid species. File Name: Aphelinus_coreae_behavior_summary.csvResource Title: Detailed behavior of female Aphelinus coreae and various aphid species. File Name: Aphelinus_coreae_behavior_detailed.csvResource Title: Summary behavior of female Aphelinus glycinis exposed to various aphid species. File Name: Aphelinus_glycinis_behavior_summary.csvResource Title: Detailed behavior of female Aphelinus glycinis and various aphid species. File Name: Aphelinus_glycinis_behavior_detailed.csvResource Title: Summary behavior of female Aphelinus rhamni exposed to various aphid species. File Name: Aphelinus_rhamni_behavior_summary.csvResource Title: Detailed behavior of female Aphelinus rhamni and aphid species. File Name: Aphelinus_rhamni_behavior_detailed.csvResource Title: README file list for Data from: Host specificity of Aphelinus species collected from soybean aphid in Asia. File Name: file_list_HostSpecificityAphelinusAsia.txt