Recognition errors by honey bee (Apis mellifera) guards demonstrate overlapping cues in conspecific recognition

Honey bee (Apis mellifera) entrance guards discriminate nestmates from intruders. We tested the hypothesis that the recognition cues between nestmate bees and intruder bees overlap by comparing their acceptances with that of worker common wasps, Vespula vulgaris, by entrance guards. If recognition cues of nestmate and non-nestmate bees overlap, we would expect recognition errors. Conversely, we hypothesised that guards would not make errors in recognizing wasps because wasps and bees should have distinct, non-overlapping cues. We found both to be true. There was a negative correlation between errors in recognizing nestmates (error: reject nestmate) and nonnestmates (error: accept non-nestmate) bees such that when guards were likely to reject nestmates, they were less likely to accept a nonnestmate; conversely, when guards were likely to accept a non-nestmate, they were less likely to reject a nestmate. There was, however, no correlation between errors in the recognition of nestmate bees (error: reject nestmate) and wasps (error: accept wasp), demonstrating that guards were able to reject wasps categorically. Our results strongly support that overlapping cue distributions occur, resulting in errors and leading to adaptive shifts in guard acceptance thresholds.