Abstract
A new species of the rarely collected neotropical microgastrine braconid wasp genus Larissimus Nixon, represented previously by only a single described species, L.cassander Nixon, was recovered by the Caterpillars and Parasitoids of the Eastern Andes in Ecuador inventory project. Larissimusnigricanssp. nov. was reared from an unidentified species of arctiine Erebidae feeding on the common bamboo species Chusqueascandens Kunth at the Yanayacu Biological Station near Cosanga, Napo Province, Ecuador. The new species is described and diagnosed from L.cassander using both morphological and DNA barcode data.