Résumé : Megaxenus Lawence, gen. nov., includes one speciesfrom North Queensland (M. Termitophilus Lawence, sp. nov.) and two from Papua New Guinea (M. bioculatus Lawence, sp. nov. and M. papuensis Lawence, sp. nov.). All three are found in the nests of Microcerotermes species and are the first known termitophiles in the family Aderidae. Notes on the behaviour and life history demonstrate that the larvae are integrated into the termite society, and are incorporated into the trophallactic feeding behaviour of termites, while the adults are actively persecuted by the termites but survive at the edges of the nest because of the webs constructed by the larvae prior to pupation. © 1990 CSIRO. All Rights Reserved.