AGGREGATION OF A LEAFMINER, CAMERARIA SP-NOV (DAVIS) - CONSEQUENCES AND CAUSES

Larvae of Cameraria sp. nov. (Lepidoptera: Gracillariidae, agrifoliella group) were highly clumped at various spatial scales among and within trees of their host-plant, Quercus emoryi. Larval distribution reflected ovipositional choice of adult females. Larval mortality increased, mainly due to interference competition, when there were >2 larvae per leaf. Mean pupal mass of survivors was inversely related to number of mines per leaf, suggesting that fecundity was decreased for larvae sharing leaves. "Winners' in aggressive encounters between larvae occupying the same leaf did not have significantly larger pupae than when both miners survived, suggesting no clear advantage in killing and cannibalizing conspecifics. The hypothesis that leafminers clump because leaves vary in phytochemical quality was not supported; density of leafminers among trees and leaves did not vary as predicted by variation in nutritional (protein and water) or "defensive' (tannin) content. Survival of leafminers in early instars was not related to phytochemistry of individual leaves. Morphological variation in leaf size and phenological variation in abscission and budbreak appeared to influence abundance, distribution and survival. Variation in these phenological factors may lead to apparent clumping either because some leaves are rejected based on size or propensity to abscise, or others are unavailable or inaccessible during the short ovipositional period. -from Author