The superfamily Platygastroidea (Hymenoptera: Proctotrupomorpha) is a diverse group of parasitoid wasps that are parasitoids of nine orders of insects as well as spiders. They appear to show a clear pattern of host group specificity among genera. A robust phylogeny is essential for devising a stable and informative classification and understanding the pattern of the shifts to parasitize new host groups. We conducted phylogenetic analyses of Platygastroidea based on four molecular markers (18S, 28S, COI and wingless) and 119 morphological characters, and a phylogenomic analysis of a subset of taxa based on 4371 single-copy, protein-coding genes. The four-gene analyses, both with and without morphological data, robustly recovered some well-established groups, e.g., Platygastridae (in its traditional sense), Scelionini, Teleasinae and Telenominae, as well as some novel patterns of relationship. The ground-plan host for the superfamily are the eggs of Orthoptera, with multiple shifts to attack new host groups. The phylogenomic analysis of a subset of taxa recovered a clear pattern of relationships for the backbone of the superfamily with maximal bootstrap support. Based on the combination of these two approaches, we present a revised classification for Platygastroidea and recognize the following eight families: Geoscelionidae stat.rev., Janzenellidae fam.nov., Neuroscelionidae fam.nov., Nixoniidae stat.rev., Platygastridae stat.rev., Proterosceliopsidae †, Scelionidae stat.rev. and Sparasionidae stat.rev.

A morphological and molecular analysis of Gryon Haliday (Platygastroidea, Scelionidae) was conducted to provide a taxonomic and phylogenetic context for a species under evaluation as a biological control agent of Bagrada hilaris (Burmeister) (Hemiptera, Pentatomidae). Our analysis revealed that Gryon is polyphyletic and that the biological control agent is not G. gonikopalense, a name that was tentatively applied to this species in 2019. We here describe this species as new, Gryon aetherium Talamas sp. nov., and resurrect the generic name Hadronotus Förster. Morphological characters that delimit our concepts of Gryon and Hadronotus are presented. Based on morphological characters and multilocus phylogenies, we determined that five presently valid scelionid genera belong within Gryon. In total, 15 species are transferred into Gryon from these genera, 215 species are transferred from Gryon to Hadronotus, and 6 species are transferred from Gryon to Dyscritobaeus Perkins. Specimens collected during field studies in California and reevaluation of specimens determined as G. myrmecophilum in Mexico reveal that G. aetherium is adventive in North America.

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The genus Pulchrisolia Szabó is revised. Pulchrisolia maculata Szabó is redescribed and nine species are described as new: P. ankremos Lahey, sp. nov. (Ghana, Ivory Coast), P. asantesanavan Noort & Lahey, sp. nov. (South Africa), P. diehoekensis van Noort & Lahey, sp. nov. (South Africa), P. ellieae Lahey, sp. nov. (Madagascar), P. nephelae Lahey, sp. nov. (Benin, Burkina Faso, Gambia, Ivory Coast, Mali, Nigeria), P. robynae van Noort & Lahey, sp. nov. (South Africa), P. sanbornei Lahey & Masner, sp. nov. (South Africa), P. teras Lahey, sp. nov. (Madagascar), and P. valerieae Polaszek & Lahey, sp. nov. (Zambia). The genus is diagnosed from Afrisolia Masner & Huggert, Isolia Förster, and Sceliotrachelus Brues, and a key is provided to the platygastrid genera of the Isolia-cluster.

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Calixomerialasalleigen. n. et sp. n. is described as a new genus and species of Sceliotrachelinae. Calixomeria most closely resembles genera of the Aphanomerus-cluster but possesses several characters that readily separate it from other sceliotracheline genera. The key of Masner and Huggert (1989) is modified to accommodate Calixomeria, and the relationship of the genus to other members of the subfamily is discussed.

The genus Alfredella Masner & Huggert is revised. Alfredella tasmanica Masner & Huggert is redescribed, Al. teres (Buhl), comb. nov. is transferred to Alfredella from Amitus Haldeman, and Al. auriel Lahey, sp. nov. (New South Wales, Tasmania) and Al. mephisto Lahey, sp. nov. (Western Australia) are described as new. The genus Masnerium Polaszek, syn. nov. is treated as a junior synonym of Amitus, and its type species, M. wellsae Polaszek, is transferred to Amitus as Am. wellsae (Polaszek), comb. nov. The relationship between Alfredella and morphologically similar genera is discussed, and a key is provided to distinguish between Aleyroctonus Masner & Huggert, Alfredella, and Amitus.

Classical biocontrol programs usually employ multiple species to control a single pest; however, the beneficial effects are not always additive due to competition between the introduced species. Knowledge of these potentially negative interactions is crucial when determining whether the introductions were successful and the extent to which they influence pest suppression. Here, we report the results of such competition between 2 exotic wasp species [Encarsia bimaculata Heraty & Polaszek and Eretmocerus sp. nr. emiratus (Hymenoptera: Aphelinidae)] introduced into Florida for control of the circumglobal super pest currently known as Middle East-Asia Minor 1, a cryptic species within the Bemisia tabaci complex (Hemiptera: Aleyrodidae). Levels of parasitism, progeny production, and host feeding were evaluated in the laboratory under various parasitoid combinations on 2 host plant species (collard and eggplant) that differed in leaf pilosity (i.e., number of trichomes on the abaxial leaf surface). Significant differences in parasitism were observed by treatment, but not host plant. Encarsia bimaculata produced fewer progeny when introduced before Er. sp. nr. emiratus on collard; however, this trend was reversed on eggplant. Eretmocerus sp. nr. emiratus produced less progeny in all combinations involving En. bimaculata on collard and when introduced before En. bimaculata on eggplant. Mortality caused by host feeding was atypical for the whiteflyparasitizing aphelinids (<5% in all treatments). Based on differences in parasitism and progeny production, no additional pest suppression would be gained by releasing En. bimaculata into an environment already under control by Er. sp. nr. emiratus.