Extracts of immunostimulated workers increases nestmate social interactions. Bees were reared in cages, 15/cage until they were 7 days old. One naïve bee was removed from each cage and coated with 5 μl of extracts from sham or lipopolysaccharide (LPS)-treated bees (one bee equivalent). After the bees were coated, each one was returned to her original cage and social interactions with untreated nestmates were monitored during a 5-minute period. Data shown represent median ± the semi interquartile range values of the aggression index, calculated from measured social behaviors . Treatment groups consisted of 12 bees coated with cuticular extracts of sham bees, and 12 bees coated with cuticular extracts from LPS-treated workers. 'LPS coating' induced significantly more interactions (agonistic) compared with the control (U = 10; P = 0.0001).