DENSITY AND PUPATION SITE OF APTEROUS FEMALE BAGWORMS, <i>METISA PLANA</i> (LEPIDOPTERA: PSYCHIDAE), INFLUENCE THE DISTRIBUTION OF EMERGENT LARVAE

Abstract

Abstract In an oil palm plantation in northeast Sumatra, Indonesia, we tested the hypotheses that selection of pupation site by female bagworms, Metisa plana (Walker), influences the distribution of emergent larvae, and that intertree dispersal by larvae is density dependant. Similar intratree distributions of empty female pupal cases and early instars and significant regressions between numbers of female pupal cases and larvae per leaf for 36 out of 39 palms indicated that larvae generally remain on the same leaf where they emerged. Proportions of early instars per female pupal case decreased with increasing densities of female pupal cases per tree and were greater on trees surrounding most heavily infested palms, suggesting that intertree dispersal of early instars is density dependent. Interspecific comparisons of life history constraints between M. plana and the allopatric bagworm Oiketicus kirbyi (Guilding) reveal different selective pressures that may have converged and favoured the development of an identical life history trait.