LIFE-HISTORY OF THE ONOPORDUM-CAPITULUM WEEVIL LARINUS-LATUS (COLEOPTERA, CURCULIONIDAE)

The population structure and stage-specific survival of the capitulum weevil, Larinus latus, a potential control agent for weedy Onopordum t histles in Australia, was studied in its native range in Greece. Altho ugh fecundity of this univoltine insect was low (35.4 eggs/female), su rvival was relatively high, with 45% of eggs reaching adulthood when p rotected from predators and parasitoids, and 23% surviving when expose d to these natural enemies. Other mortality factors of importance for immature stages were a failure to establish, due largely to ovipositio n by females on inappropriate sites on the thistle capitula, and inter - and intraspecific competition for larval resources. Once emerged, ad ult losses due to overwintering mortality and net migration were estim ated at a further 48%. Despite these losses there was a net doubling o f the population at the study site between Onopordum flowering seasons . The data suggest that movement of adults occurs both within and betw een patches and that variability in population size relative to the re source base is low. Overall, L. latus may be considered a K-strategist which forms relatively stable populations over a fragmented habitat a nd which maintains its population integrity through a certain degree o f annual redistribution. The implications of these data for the potent ial effectiveness of L. latus as a biological control agent of weedy O nopordum spp. are discussed.