Age-dependent changes in juvenile hormone esterase and general carboxyesterase activity in the hemolymph of the colorado potato beetle, Leptinotarsa decemlineata.

An in vitro method has been developed for the quantitative estimation of juvenile hormone (JH) esterase activity in the hemolymph of the Colorado beetle Leptinotarsa decemlineata Say. The apparent Km value for JH-esterase was determined. JH-esterase and general carboxyesterase activities were estimated throughout the life cycle and under different photoperiodic conditions. High activities were observed in fourth instar larvae and in beetles just before diapause. Lower activities were found in third instar larvae, long-day, diapause and post-diapause beetles. Similar variations were found in general carboxyesterase activity but not in protein concentration. A possible role for the esterase in the regulation of the JH titer is discussed.