Characterization of the genus Hypomicrogaster Ashmead (after Valerio & Whitfield 2015).
HEAD. Antennal placodes present as two ranks on proximal flagellomeres, middle flagellomeres with placodes equal in shape dorsally and ventrally; glossa truncate; postgena nitid and highly concave with concavity reaching the posterior ocellus; ocelli forming a low triangle. Gena punctate and with transverse longitudinal lineate sculpture on distal edge and basal 2/3 of postgena. MESOSOMA. Pronotum with two lateral grooves (ventral and dorsal); propleuron with a upwardly projecting flange on posterior dorsal edge; epicnemial carina absent; mesonotum without notauli; scutellar lunulae with a well-defined triangular shape, nitid along with scutellar distal edge; scutellum medial area on distal edge with two large costulae with a few to numerous setae present below; metanotum anterior edge well appressed to scutellum and not exposing phragma, sublateral setae present as tuft; propodeum with anterodorsal area reduced and angled to posterior area about mid length, medial longitudinal carina typically present (in some cases absent, thus areola not divided by it), areola well-defined and closed normally but sometimes totally absent or present only as small carinae diverging from distal area of propodeum, transversal carina typically present with or without accompanying sculpture, in some species absent; costulae normally present but in some cases totally absent. LEGS. Hind coxae elongate, reaching to beyond second metasomal tergite; tarsal claw normally with basal tooth, but sometimes this is very reduced or in some cases the claw exhibits a conspicuously developed basal lobe instead of the usual basal long seta (two species however with a pectinate tarsal claw); fore telotarsus usually normal with a long thin seta but in some species excavated apicoventrally and with long broad sinuate seta, sometimes middle and hind telotarsus also with long and broad seta(e) and highly modified and excavated with sinuate long setae. WINGS. Fore wing: Vein 3Rs weakly curved; vein (1M+1Rs) angled between 20° and 60°; small to moderate-sized areolet normally with vein r-m meeting 2Rs, sometimes not closed distally; vein 2A absent. Hind wing: vein r spectral; cells 1R and 2R with almost the same width; vein 2r-m spectral; vein 2A absent; veins 2Cu and cu-a slightly concave but not sinuate in shape; vannal lobe separated from remainder of wing by a clearly defined notch, margin after widest point distally flattened or slightly concave, without setosity normally, but sometimes conspicuously setose throughout with long or short setae. METASOMA. First tergum with basal excavation present and without mediobasal longitudinal groove, apical section flat to slightly arched without any medioapical excavation, broad but sometimes narrow with lateral edges subparallel; junction of metasoma terga 1–2 flexible; second tergum normally strongly and transversely rectangular in shape but sometimes with subtriangular shape and wider than long; junction of tergum 2 to 3 represented by a fine distinct suture; metasoma not carapace-like; hypopygium medially strongly desclerotized and longitudinally folded into pleats when ovipositor is long, but when ovipositor short then more or less desclerotized medially and sharply folded medially without pleats; ovipositor sheaths with setae distributed throughout their lengths, variable in length (from 1/3 to more than 2x length of hind tibia), attached to second valvifer near apex on ventral side; ovipositor tapered throughout its length but sometimes short, laterally compressed and abruptly narrowing at or just beyond midlength; 8th metasomal tergite of females 2x to 4x taller than long, second valvifer tall, lorate and not expanded apically. LARVA. According to Mason (1981) the larva exhibits mandibles each with a long blade bearing about 20 long teeth; palpi long; labium with 2–4 setae and each maxilla with one seta. In addition, the larval skin bears long spine like setae (Mason 1981, Fig. 105). However, the larvae of the species with setose vannal lobes are currently unknown, so these characterizations might not hold throughout the genus (see further in text).
Quick diagnosis. Lunuale very conspicuously triangular in shape plus postoccipital area very convex in shape and nitid (in dorsal view), almost reaching the posterior ocelli, propodeum with a defined areola that normally is divided by the midlongitudinal carinae (most of the time evident). If areola partially or totally absent then the following combination applies: shape of the postocciput extremely concave and nitid, almost reaching the posterior ocelli, second submarginal cell of fore wing closed distally and lunulae triangular in shape plus a very setose and even vannal lobe fringe.
Additional comments. The last review of the genus (Valerio & Whitfield 2015) described 40 new species, synoymized 10 species, and transferred one species (from Microgaster to Hypomicrogaster). But there is still work to do, as eight species, currently under Hypomicrogaster and described by Nixon in 1965 are actually better placed in Choeras (those species were described by Nixon mostly as part of his species-groups vacillatrix and psarae). After studying further Nixon's material, those changes will be formally proposed in a future paper, along with pictures and details of each species.