The nest-exchange technique was employed on colonies ofBelonogaster juncea junceato study the degree of nest and immature brood recognition in adults. In each experiment two nests, approximately at the same stage of development and found in the field, were exchanged and the behaviour of the females was recorded before and after their substitution. Checking the nests 24 hr after the exchange showed that all the experimental nests had been accepted by the alien females and that a portion of the eggs and immature larvae had been destroyed. It seems that just one female on each nest is responsible for destroying the immature brood. None of the behaviours performed by the females suggested that they applied secretion over the nest surface and immature brood. From the results of the experiment, it appears that a nest and brood recognition mechanism exists in this species, which is probably based on characteristic odours.