REPELLENCY OF ORAL EXUDATE TO EASTERN AND WESTERN SPRUCE BUDWORM LARVAE (LEPIDOPTERA, TORTRICIDAE)

A two-choice feeding bioassay was used to investigate the intra-specif ic repellency of the larval oral exudate of eastern and western spruce budworms, Choristoneura fumiferana (Clem.) and C occidentalis Free., respectively. Results of the bioassay indicated that feeding behavior on artificial diet-drop feeding stations was modified in the presence of exudate, with feeding stations treated with conspecific exudate bei ng avoided when an untreated station was available 3 cm away. Feeding was suppressed when a single, exudate-treated station was provided, or when the treated and untreated stations were separated by only 1 cm. The repellent effect functioned both inter- and intraspecifically. Whe n induced to produce exudate, C. occidentalis larvae were not immediat ely repelled by either their own or other individuals' exudate. Howeve r, 24 hr after induction, test larvae were repelled by exudate from ei ther source. In both species, larval oral exudate probably functions t o repel conspecific competitors.