The larva of Popanomyia kerteszi James & Woodley is described based on individuals collected under tree barks in initial stages of decomposition in Marambaia island (23º04'15''S, 43º53'59''W, at sea level), Rio de Janeiro state, Brazil. The immatures of P. kerteszi were compared with other species of the subfamily Pachygastrinae and an identification key to the described immature stages of this subfamily is presented. This is also the first record of P. kerteszi to Rio de Janeiro.
Brazil; Neotropical; new record; taxonomy
