Juvenile hormone (JH) is a major player in caste development and division of labor in the honey bee. To investigate how titer levels are controlled we searched the honey bee genome sequence for a candidate insect juvenile hormone esterase (JHE) gene. Developmental expression profiles for this A. mellifera JHE (Amjhe) established by RT-PCR varied in accordance with the hemolymph JH titer in both queen and worker larvae, revealing that high expression levels in last instar larvae correlated with marked declines in the JH titer. For functional validation of this putative JHE we employed an RNA interference strategy in adult workers. Four day-old worker bees were injected with 10 µg of JHE dsRNA or with 10 µg GFP dsRNA (control). The bees were sampled five days later for quantification of AmJHE mRNA levels by quantitative RT-PCR and for RIA measurement of their respective JH titer. JHE knockdown bees (n=7) had a much higher JH titer than GFP controls (n=8) or untreated bees (n=8) (ANOVA; P<0.001) verifying the JH degradation function of this putative AmJHE and suggesting that it may indeed play a major role in caste development and division of labor. Funded by FAPESP