Search

The discrimination of nestmates is an important requisite to avoid exploitation by unrelated individuals. Although recognition among adult social wasps has been examined in detail, few studies have investigated brood discrimination by adults. Adult females of somePolistesspecies were previously shown to discriminate their nestmate larvae on the basis of cuticular hydrocarbons. However, nestmate larval discrimination has not been studied in polygynous swarm-founding wasps of the tribe Epiponini. Whether the workers ofPolybia paulistarecognised their own larvae when presented outside the nest comb was investigated in the present study. We also compared the cuticular chemical profiles of 5th instar larvae from different colonies. Workers did not bite non-nestmate larvae more frequently than their nestmate larvae. However, they spent significantly more time licking with their nestmate larvae than with non-nestmate larvae. These behavioural tests suggest that the workers ofP. paulistamay have the ability to distinguish between larvae from their own colony and alien larvae. The epicuticle of larvae had 69 compounds consisting of linear and methyl branched compounds with chains from 19 to 36 carbon atoms. Analyses of the cuticular extracts of 5th instar larvae from the experimental colonies significantly allocated (100%) in their predicted groups, suggesting that discrimination of own larvae by the workers may be mediated by colony-specific, larval-borne cues. These results suggest that workers of the swarm-founding waspP. paulistarecognised the larvae of their own nest from alien larvae according to distinct cuticular chemical profiles. Because it is not so far known that swarm-founding wasps exhibit intraspecific colony usurpation, this discrimination is not used in their colonial life even if workers recognise the chemical cues between more or less related larvae. Our results also imply that nestmate larval recognition could be evolved in colonies with many matrilines, asP. paulistacolonies have. [ABSTRACT FROM AUTHOR]

Division of labor is one of the most striking features in the evolution of eusociality. Juvenile hormone (JH) mediates reproductive status and aggression among nestmates in primitively eusocial Hymenoptera (species without morphologically distinct castes). In highly social species it has apparently lost its gonadotropic role and primarily regulates the division of labor in the worker caste. Polybia occidentalis, a Neotropical swarm-founding wasp, is an ideal model to understand how JH levels mirror social context and reproductive opportunities because of the absence of a clear morphological caste dimorphism. In this study, we tested the hypothesis that JH influences division of labor, ovary activation and cuticular hydrocarbon profiles of workers. Our observations confirmed that a JH analog (methoprene) and an inhibitor of JH biosynthesis (precocene) affected the cuticular chemical profile associated with age polyethism. Also, methoprene and precocene-I treatment of females influenced ovarian activation differently (individuals treated with methoprene expressed more activated ovaries while precocene treatment did not have significant effect). These results suggest that different hormonal levels induce a differential expression of cuticular chemicals associated with workers' age polyethism, which may be essential for keeping the social cohesion among workers throughout their lives in the colony. Furthermore, JH is likely to play a gonadotropic role in P. occidentalis. JH has apparently undergone certain modifications in social Hymenoptera, presenting multifaceted functions in different species., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2021. Published by The Company of Biologists Ltd.)