Monoterpenes,source of the distinctive odor of conifers,are generally considered plant defensive compounds.However,they are also known to act as long-range insect attractants,as they are volatile and permeate forest airspaces.Moreover,they are lipid soluble and can be absorbed into plant epicuticular waxes.We test their role in short-range host plant choice by both adult females and larvae of a folivorous forest pest (Choristoneura fumiferana).We conducted laboratory assays testing the responses of Easte spruce budworm to an artificial monoterpene mix (α-pinene,β-pinene,limonene,myrcene) and to white spruce (Picea glauca) epicuticular waxes in closed arenas.Ovipositing females preferred filter paper discs treated with P glauca waxes to controls,and preferred the waxes + monoterpenes treatment to waxes alone.However,females showed no preference between the monoterpene-treated disc and the control when presented without waxes.Feeding larvae prefered wax discs to control discs.They also consumed discs treated with realistic monoterpene concentrations and wax preferentially over wax-only discs,but showed no preference between extremely high monoterpene concentrations and wax-only controls.In an insect-free assay,P.glauca epicuticular wax decreased monoterpene volatilization.These results suggest that P.glauca waxes and realistic concentrations of monoterpenes are stimulatory to both egg-laying females and feeding larvae,and that their effects are synergistic.