Cohen, E., Gerson, U. and Mozes-Koch, R., 1993. Epoxide hydrolase in the bulb mite Rhizoglyphus robini: properties and induction, 1993. Exp. Appl. Acarol. 17: 381-392.Using styrene oxide as substrate, most of the epoxide hydrolase (EH) activity monitored in the bulb mite Rhizogt)phtt~ robini was associated with the microsomal compartment. The microsomal and cytosolic EHs did not display any significant preference in hydrating trans stilbene oxide (TSO) and cis stilbene oxide (CSO). The microsomal EH, which has a Km'value of 5×IO-~M and pH optimum of 7.8, was sensitive to ethanol and its activity was inhibited to a moderate extent by 4-fluorochalcone oxide, TSO, CSO and trans-chalcone oxide at a level of IO-4M. Microsomal EH was considerably induced (4--5-fold) in mites feeding garlic and onion, or ingesting TSO-impregnated filter papers. Other epoxides like CSO, 2,4-dichlorostilbene oxide, methyl chaicone oxide and heptachlor epoxide displayed moderate induction levels (1.4-2.6-fold). Of the toxicants assayed only sodium phenobarbital was a potent inducer. Lindane, malathion and DDT did not stimulate EH activity and 3-methylcholanthrene was even inhibitory. A decrease in EH activity was observed with a number of phytochemicals tested such as sinigrin, flavone, menthol, trans-[5-carotene, chalcone, aUyl sulphide and trans-cinnarrfic acid.