The types and undescribed material of the hymenopteran fossils of the Insect Bed of the Bembridge Marls from the Isle of Wight (UK) are critically revised and studied. A total of 1460 fossils are recorded and attributed to 20 families: Gasteruptiidae s.l. (1); Proctotrupidae (3); Diapriidae (24); Cynipidae (7); Figitidae (6); Pteromalidae (1); Agaonidae (3); Scelionidae (12); Platygastridae (2); Ichneumonidae (32); Braconidae (75); Bethylidae (3); Crabronidae (2); Sphecidae (1); Apidae (2); Scoliidae (1); Tiphiidae (2); Vespidae (4); and Formicidae (1220). Described as new are 51 species, 13 genera, two tribes and two subfamilies. Minimum number of species recorded (either as described species or representing higher taxa with no described species in the assemblage) is 118. The composition of the hymenopteran assemblage is most similar to that of Baltic amber and indicative of a well forested territory, as well as of a humid, equable (aseasonal but not very hot) climate, more typically equable than in the Baltic amber source area, judging from the absence of Aphidiinae and scarcity of aphids.

The parasitoid wasp family Ichneumonidae is arguably one of the groups for which current knowledge lags most strongly behind their enormous diversity. In a five-day meeting in Basel (Switzerland) in June 2019, 22 researchers from 14 countries met to discuss the most important issues in ichneumonid research, including increasing the speed of species discovery, resolving higher-level relationships, and studying the radiation of these parasitoids onto various host groups through time. All agreed that it is time to advertise ichneumonid research more broadly in the scientific community and thereby attract young talents to this group for which specialists are sorely lacking. In order to popularize the group, we here suggest a new name for the family, “Darwin wasps”, to reflect the pivotal role they played in convincing Charles Darwin that not all of creation could have been created by a benevolent god. We hope that the name catches on, and that Darwin wasps start buzzing more loudly across all disciplines of biology.

Two Costa Rican genera, Megalochus gen. nov. and Stethantyx Townes, are revised. These genera comprise a distinctive generic group that we refer to as the Stethantyx genus-group, veins Rs+2r and Rs angled more than 90°, vein 2rs-m and abscissa of M between 2rs-m and 2m-cu not or very weakly thickened, hind wing with vein cu1&cu-a (nervellus) more or less vertical, and prepectal carina with upper end not reaching anterior margin of mesopleuron, continuing above and backwards to the subtegular ridge. Both genera include medium sized to large species with body length 4.0 to 15.0 mm. Megalochus comprises only the type species, M. grandis sp. nov., occurring in Costa Rica, Ecuador and southern Brazil. It is the largest representative of the subfamily, with a body length of 10.5 to 15.0 mm. Megalochus differs from Stethantyx, besides the larger body size, by the slenderer first metasomal segment, which is round in cross-section and lacking glymmae, propodeum and metapleuron with coarse rugae, and shortened antennae with strongly transverse flagellomeres. Stethantyx is the dominant, most species-rich genus in the Costa Rican tersilochine fauna and probably in the Neotropical region. Twenty two species of this genus were discovered in

Resumen. Los ichneumónidos integran la familia con mayor diversidad de especies en el orden Hymenoptera y una de las más diversas en la clase Insecta. Para México se registran 1 291 especies (5.3% del total mundial) de 300 géneros y 28 subfamilias, con 43 géneros por identificar sus especies, para un total de 343 géneros. Se estiman entre 3 215 y 4 544 especies para el país, considerando la necesidad de más estudios en las regiones norte, centro, occidente y sureste. El 59% (760) de las especies son neotropicales, el 29% (371) son neotropicales y neárticas, el 10% (127) son neárticas y el 2% restante (33) tiene otra distribución. De momento, 45% (580) de las especies se consideran endémicas, situación que se debe a la descripción reciente de muchas especies nuevas y a la falta de más estudios en Centroamérica (excepto Costa Rica).

Abstract-Based on a large number of specimens deposited in many collections, and on material