Altered juvenile hormone dynamics mediate earlier foraging in Nosema-infected honey bees

Abstract Parasites can profoundly alter host behavior, yet the physiological mechanisms underlying these changes are often unclear. In honey bees (Apis mellifera), microsporidian infection has long been associated with precocious foraging, a life-history shift that can destabilize colony function. Here we identify the endocrine mechanism linking infection to behavioral maturation. Using Nosema apis, we show that infected workers initiate foraging significantly earlier than controls across four colonies (hazard ratio = 2.69, p < 0.001). This behavioral acceleration was accompanied by a ~1.7 fold increase in circulating juvenile hormone (JH) titers, an ~83% increase in JH biosynthesis by the corpora allata (CA), and increased in vivo JH metabolism, causing elevated JH turnover during infection. Crucially, surgical removal of the CA eliminated the significant effect of infection on foraging, supporting the hypothesis that activation of this gland contributes to the behavioral effects of infection. Together, these results reveal that microsporidian infection accelerates honey bee behavioral maturation by increasing JH turnover through activation of the CA.