Eustochomorpha Girault, with one described species, E. haeckeli Girault, from Australia is redescribed. Neotriadomerus Huber, gen. n., is described, together with seven new species, all from Australia: N. burwelli Huber, sp. n., N. crassus Huber, sp. n., N. darlingi Huber, sp. n., N. gloriosus Huber, sp. n., N. longiovipositor Huber, sp. n., N. longissimus Huber, sp. n. (one of the largest species of Mymaridae), and N. powerae Huber, sp. n. Proarescon Huber, gen. n., is described for P. primitivum (Huber), comb. n., transferred from Borneomymar Huber, and P. similis Huber, sp. n., from Thailand. The previously unknown male of Borneomymar madagascar Huber is described and the genus is redescribed from critical point dried and slide mounted specimens. Triadomerini, stat. n., is proposed to include six genera: Borneomymar, Eustochomorpha and Neotriadomerus, and the Cretaceous Carpenteriana Yoshimoto, Macalpinia Yoshimoto and Triadomerus Yoshimoto. Aresconini is proposed to include five (possibly six) genera: Arescon Enock, Kikiki Huber and Beardsley, Proarescon Huber and Tinkerbella Huber and Noyes, and the Cretaceous Myanmymar Huber and, tentatively, also Enneagmus Yoshimoto. The two tribes are proposed as being the earliest lineages in Mymaridae, with Neotriadomerus and Triadomerus being sister genera to the remaining extant and extinct genera, respectively.