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Individual recognition (IR) has been demonstrated in some Pachycondyla ants. The maintenance of such memories is challenged when queens are separated for the few hours of forage (attenuation) or when they are simultaneously interacting with conspecifics in a reduced space, that is, the nest (interference). By quantifying the level of aggression among familiar and unfamiliar queens of P. inversa, we showed that memories of social partner's identity are robust to attenuation over the course of 2 days and to interference from subsequent interaction with five other individuals. Because wasps and crabs also remember familiar partners after separation and interaction with other conspecifics, we propose that robustness of social memories is widespread in invertebrates with IR abilities. [ABSTRACT FROM AUTHOR]

[Display omitted] • Foragers had a higher immune response than guards, regardless of their age. • Foragers had similar immune responses to nurses. • Immune response declined with age in wasps that did not specialize behaviorally. • Behavioral modulation of immune response can overcome immunosenescence. Workers of social hymenopterans (ants, bees and wasps) display specific tasks depending on whether they are younger or older. The relative importance of behavior and age in modulating immune function has seldom been addressed. We compared the strength of encapsulation-melanization immune response (hereafter melanotic encapsulation) in paper wasps displaying age polyethism or experimentally prevented from behavioral specialization. Foragers of Polybia paulista had higher melanotic encapsulation than guards, regardless of their age. Nevertheless, melanotic encapsulation decreased with age when wasps were prevented from behavioral specialization. Thus, in this species, worker melanotic encapsulation seems more sensitive to task than age. Foraging is considered one of the riskier behaviors in terms of pathogen exposure, so upregulating melanotic encapsulation in foragers can possibly improve both individual and colony-level resistance against infections. [ABSTRACT FROM AUTHOR]

Conventional signals are maintained via social costs and commonly used in the animal kingdom to assess conspecifics' agonistic ability during disputes over resources. In the last decade, some experimental studies reported the existence of visual conventional signals in several social wasp species, being good rank predictors in different social contexts. Females of the social wasp Polistes gallicus do not cooperate to start nests but they often try to usurp conspecific nests. Here, we showed that the reproductive females of this species have variable facial colour patterns that function as conventional signals. Wasps with larger black spots on their clypeus are more likely to successfully overwinter, are larger, and are better at fighting and at holding a nest. Furthermore, in field experiments, resident foundresses rely on facial pattern to assess usurpers' fighting abilities, modulating their defence reaction accordingly, so that rivals with larger black spot receive more aggression than rivals with smaller or no black spots on the clypeus. Our study reveals that visual recognition abilities are widespread among paper wasps that, regardless of their social biology, face similar selective pressures within competitive contexts. [ABSTRACT FROM AUTHOR]