Abstract
A new species of microgastrine wasp, Cotesiacassina Salgado-Neto, Vásquez & Whitfield, sp. nov., is described from southwestern Colombia in Tumaco, Nariño. This species is a koinobiont gregarious larval endoparasitoid, and spins a common mass of cocoons underneath the host caterpillars of Opsiphanescassina (Felder & Felder) (Lepidoptera, Nymphalidae), feeding on oil palm trees (interspecific hybrid Elaeisoleifera × E.guineensis) (Arecaceae). While superficially similar, both morphologically and biologically, to C.invirae Salgado-Neto & Whitfield from southern Brazil, the two species are distinct based on DNA barcodes, host species, geographical range and morphological characters.