none no species Since its introduction into southern Florida at the beginning of this century, the Australian paperbark tree, Melaleuca quinquenervia (Cav.) S. T. Blake, has become a major economic and environmental pest. A project to develop biological control agents for this tree in Australia began in 1986. Among a number of potential agents, a defoliating sawfly, Lophyrotoma zonalis (Rohwer) (Hymenoptera: Pergidae), was selected for further study. The larvae of this sawfly are conspicuous defoliators of Melaleuca trees in northern Queensland. We collected these sawflies from Cairns to Mackay in northern Queensland, and they are also known from the Northern Territory and New Guinea. The life-cycle from egg to adult takes about 12 weeks. The egg, larval and pupal stages are parasitized by dipteran and hymenopteran parasites. We conducted 2234 larval no-choice feeding tests on 46 plant species from 20 families. Although feeding occurred on 35 of these plant species, M. quinquenervia and its close relative, M. leucadendra (L.) L., were preferred. In oviposition tests, larvae only emerged from egg cases laid on M. quinquenervia and M. leucadendra. Our extensive field surveys of nearly 70 tree species found L. zonalis eggs and larvae only on several closely related Melaleuca species. The potential effectiveness of this sawfly as a biocontrol agent is discussed and estimated using the Goeden-Harris scoring system. Quarantine studies of this insect began in Florida in early 1994. Nutrition; Feeding behaviour; Life cycle and development; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Ecology; Population dynamics; Land and freshwater zones; Australasian region; Australia; Nearctic region; North America; USA Tachinidae; Aprix (Ichneumonidae ); Eulophidae; Hymenopteran hosts; Lophyrotoma zonalis; Mortality factor for immature life stages of host; Queensland; Mortality factor for immature life stages of hymenopteran host Lophyrotoma zonalis (Pergidae); Food preferences; Plant host range, laboratory study & Queensland; Life cycle, plant host; Dipteran parasites; Tachinidae; Hymenopteran parasites; Aprix & Eulophidae; Mortality factor for immature life stages; Plant hosts; Melaleuca quinquenervia (paperbark tree), parasites & host range; Mortality; Hymenopteran & dipteran parasitism of immature stages; Queensland; Life history, parasites & plant host range, potential control agent; Florida; Potential control agent of plant pest, evaluation