Identification keys for females, and for males where known, to the 39 genera and 11 subgenera of Mymaridae in America north of Mexico are given. The genera are illustrated with over 1010 photographs and/or scanning electron micrographs. The 202 currently named and valid species reported from America north of Mexico are catalogued. Reliable host records are reported for 16 genera and almost 90 species from rearings in the region. The five genera represented by more than one subgenus in the region are: Anagrus Haliday, Anaphes Haliday, Erythmelus Enock, Kalopolynema Ogloblin, and Polynema Haliday. Five other genera are represented only by unnamed and possibly undescribed species. About 1000 literature references, mainly the North American ones, are listed. Three new species are described: Callodicopus floridanus Huber, sp. n., Neostethynium americanum Huber, sp. n., and Stephanocampta xanthogaster Huber, sp. n. Cosmocomoidea marilandica (Girault), stat. rev., is placed in synonymy under C. dolichocerus (Ashmead). Platypatasson Ogloblin is given subgeneric status as Platystethynium (Platypatasson Ogloblin), stat. rev. Corrections and additions to the mymarid fauna of Mexico by Guzmán-Larralde et al. (2017) are also given.

Separate identification keys for females, and for males where known, of the 40 genera of Mymaridae (Hymenoptera: Chalcidoidea) in the Afrotropical region are given. The subgenera of four genera are also included in the key to females. The genera are illustrated with over 300 photographs. The 122 named, valid species reported from the region are catalogued. Reliable host records are reported for 6 genera and 11 species from rearings undertaken in the region. An appendix lists the 27 species from northern Africa and offshore islands (Canary Islands, Madeira) but not recorded in the Afrotropical region as defined in this publication. Camptoptera (Zemicamptoptera) Ogloblin & Annecke, syn. n. is synonymized with Camptoptera (Camptoptera) Foerster. Eofoersteria Mathot, syn. n. is synonymized with Camptoptera Foerster and is treated as subgenus C. (Eofoersteria) Mathot, stat. n.; its type species Eofoersteria camptopteroides Mathot is transferred to Camptoptera as C. (Eofoersteria) camptopteroides (Mathot), comb. n. Polynema megacephala (Risbec) is transferred to Lymaenon as L. megacephala (Risbec), comb. n. Limacis opuntiae Risbec is transferred to Encarsia Foerster (Hymenoptera: Aphelinidae) as E. opuntiae (Risbec), comb. n. A few corrections to Huber et al. (2020) are given.

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Platystethynium (Platypatasson) earlyi Huber, sp. n. (Hymenoptera: Mymaridae), is described from both sexes reared from an egg of Rhaphidophoridae (Orthoptera) found in an old mining tunnel in New Zealand. The male is micropterous and has lateral ocelli but no median ocellus, a unique feature in Mymaridae found so far only in males of Platystethynium Ogloblin species. The remaining described Eastern Hemisphere species of Platystethynium are discussed and Platystethynium glabrum Jin & Li, syn. n., is placed in synonymy under P. onomarchicidum Ogloblin. A key to females, and males where known, of the described Eastern Hemisphere species of Platystethynium is given.

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