Speed and accuracy in nest-mate recognition: a hover wasp prioritizes face recognition over colony odour cues to minimize intrusion by outsiders

Abstract

Social insects have evolved sophisticated recognition systems enabling them to accept nest-mates but reject alien conspecifics. In the social wasp, Liostenogaster flavolineata (Stenogastrinae), individuals differ in their cuticular hydrocarbon profiles according to colony membership; each female also possesses a unique (visual) facial pattern. This species represents a unique model to understand how vision and olfaction are integrated and the extent to which wasps prioritize one channel over the other to discriminate aliens and nest-mates. Liostenogaster flavolineata females are able to discriminate between alien and nest-mate females using facial patterns or chemical cues in isolation. However, the two sensory modalities are not equally efficient in the discrimination of 'friend' from 'foe'. Visual cues induce an increased number of erroneous attacks on nest-mates (false alarms), but such attacks are quickly aborted and never result in serious injury. Odour cues, presented in isolation, result in an increased number of misses: erroneous acceptances of outsiders. Interestingly, wasps take the relative efficiencies of the two sensory modalities into account when making rapid decisions about colony membership of an individual: chemical profiles are entirely ignored when the visual and chemical stimuli are presented together. Thus, wasps adopt a strategy to 'err on the safe side' by memorizing individual faces to recognize colony members, and disregarding odour cues to minimize the risk of intrusion from colony outsiders.

Keywords: chemical cues; cognitive abilities; multimodal sensory cues; trade-offs; visual cognition; visual cues.

Figure 1.

Liostenogaster flavolineata females' portraits representing some examples of different facial patterns present in the species. The bar indicates 1 mm in length. (Online version in colour.)

Figure 2.

Comparison between the average number of bites directed by resident females towards a nest-mate visual stimulus (nest-mate wasp deprived of its CHCs), alien visual stimulus (alien wasp deprived of its CHCs), a nest-mate chemical stimulus (nest-mate CHCs extract applied on a square piece of filter paper) and an alien chemical stimulus (alien CHCs extract applied on a square piece of filter paper). Box plots show medians, 25th and 75th percentiles.

Figure 3.

Average number of bites shown by resident females reacting towards a full alien and a full nest-mate lure (alien and nest-mate washed wasp reapplied with own CHCs extract, respectively), and two crossed lures (a nest-mate washed wasp reapplied with alien CHCs extract and an alien washed wasp reapplied with alien CHCs extract).