A multi-trait view of juvenile hormone pleiotropy in a highly eusocial wasp

Juvenile hormone (JH) is a conserved endocrine regulator that coordinate reproduction, behaviour and chemical communication in social insects. We tested whether JH would regulate these effects in queenright colonies of the common wasp Vespula vulgaris. We experimentally manipulated JH signalling in newly emerged workers using methoprene (JH analogue) or precocene (anti-JH), and measured ovarian development, task performance and cuticular hydrocarbon (CHC) profiles. As expected, ovarian activation increased with age and was altered by methoprene treatment accelerating early oocyte development, but these treatment effects changed later in life. Task allocation showed the expected age-related shift from intranidal to extranidal activities, however, was only weakly affected by the treatment. By contrast, CHC profiles varied with age, task and hormonal manipulation. Age had the broadest chemical effect, task differences mainly separated intranidal from extranidal workers, and treatment affected several compounds previously associated with fertility signalling, including long-chain alkanes. These results indicate that the experimental manipulation of JH-related signalling affected reproductive physiology and chemical phenotype, while overt task allocation remains primarily age structured. Hormonal pleiotropy may therefore contribute to the partial coordination of fertility, maturation and chemical communication in workers of V. vulgaris, but its effects appear to be trait-specific rather than uniform across all aspects of the worker phenotype.