WEEVIL PHYSIOLOGY CONTROLS THE FEEDING RATES OF PISSODES STROBI ON PICEA-SITCHENSIS

The number and volume of feeding and oviposition holes made by female white pine weevils, Pissodes strobi (Peck), on lateral branches of res istant and susceptible Sitka spruce, Picea sitchensis (Bong.) Carr., w ere determined. When all possible effects of weevil reproduction on fe eding rates were eliminated, by using reproductively noncompetent weev ils, there was no significant difference in the number of feeding hole s made on the two host types. In addition, the volume of feeding holes was unaffected by host type on day 1. In contrast, when differential reproductive activity was induced by treating weevils with juvenile ho rmone, and the host factor was eliminated, by using only the susceptib le host, higher reproductive activity was accompanied by a significant ly larger number of feeding holes. Hormone treatment also led to an in crease in the volume of feeding holes in the absence of any influence of host factors. Results are interpreted in relation to the direct eff ects of host resistance on feeding rates (which determine host accepta bility); and the indirect effects of host resistance on feeding rates mediated through the physiology of the weevils (which determine host s uitability). Our results show that both the number of feeding holes an d their volume are determined primarily through weevil metabolism.