﻿AbstractA new species of the rarely collected neotropical microgastrine braconid wasp genusLarissimusNixon, represented previously by only a single described species,L.cassanderNixon, was recovered by the Caterpillars and Parasitoids of the Eastern Andes in Ecuador inventory project.Larissimusnigricanssp. nov.was reared from an unidentified species of arctiineErebidaefeeding on the common bamboo speciesChusqueascandensKunth at the Yanayacu Biological Station near Cosanga, Napo Province, Ecuador. The new species is described and diagnosed fromL.cassanderusing both morphological and DNA barcode data.