Mapping social behaviour. Social insects should be faithful to their nests because they gain genetic fitness benefits from raising kin. Yet, monitoring the movements of individually radio-tagged wasps reveals that 50% of paper wasp workers 'drift' between different nests: workers appear to help raise related brood on the nests they visit. These social networks, mapped from the movements of 455 radiotagging wasps from 32 nests (represented as nodes in the map), show the relative drifting rates (represented as the 'edges' or lines in the map) of tagged workers between nests within 4 nest aggregations. Without radio-tagging technology, these maps could not have been generated, and hence a potentially important aspect of social behaviour would have gone unnoticed.