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A biphasic increase of hemolymph glucose levels was observed following injection to bees of cupric gluconate or sulfate, both potent agents for the control of Varroa jacobsoni, a parasitic mite of hives. The simultaneous injection to bees of 0.3 microM BAYg5421 (an inhibitor of alpha-glucosidases) quenched the response, suggesting a direct effect of 2 nmol/bee cupric ions on trehaloses' activity. One nanomol of injected cupric gluconate increased the trehalose (Tre) activity by 233% in crude hemolymph extracts at 1 mM trehalose concentration, and exhibited biphasic dose-related effects with a maximum 15% increase at 0.5 mM cupric ion and a stabilized 20% inhibition from 4 mM, regardless of the anionic moiety. Upon partial purification of the enzyme complex, two fractions (FI = 75% and FII = 25% of total activity) were isolated that exhibited, respectively, less and more marked positive cooperatively than crude extract. Form I showed almost no susceptibility to either cupric derivatives, which indicated form II as the most likely target, with 68% and 72% increases with 0.25 mM cupric sulfate and 0.5 mM cupric gluconate, in presence of 16 mM trehalose.