May function as a juvenile hormone (JH)-specific degradation enzyme in vivo decreasing JH activity. Hydrolyzes JH III in vitro. Hydrolyzes effectively also methyl hepthylthioacetothioate (HEPTAT), a synthetic substrate. Of the general esterase substrates, it has preference for 2-naphthyl acetate (2-NA) and shows a weak activity for 1-NA and 4-nitrophenylacetate (4-NPA). H2O + juvenile hormone III = H(+) + juvenile hormone III carboxylate + methanol Inhibited by 3-octylthio-1,1,1-trifluoro-2-propanone (OTFP), a specific inhibitor of juvenile hormone esterase (JHE), but not by diisopropyl fluorophosphate (DFP), a serine enzyme inhibitor. kcat is 0.164 sec(-1) for JH III. Low expression in first to third larval instars, but substantially higher expression levels detected at the beginning of the sixth (penultimate) instars. Strongly expressed in seventh (final) instar larvae. High levels of expression are detected on the final day of pupal development in both males and females. On the seventh day of adult life, the levels in females are greater than those in males by a factor of more than three. Belongs to the type-B carboxylesterase/lipase family.