FACTORS INFLUENCING OVIPOSITION, LARVAL GROWTH AND MORTALITY IN CHRYSOMYA-MEGACEPHALA (DIPTERA, CALLIPHORIDAE), A PEST OF SALTED DRIED FISH IN SOUTH-EAST ASIA

Laboratory investigations were conducted into factors affecting oviposition, larval growth and mortality in the blowfly Chrysomya megacephala (Fabricius), an important cause of losses of salted dried fish in south-east Asia. When presented with a choice of fish spiked with recently laid C. megacephala eggs and unspiked fish, the flies preferentially oviposited on the spiked fish. Subsequently choice experiments indicated that the attraction exerted by the eggs was mainly olfactory in nature. When presented with oviposition media of a range of salt concentrations, C. megacephala preferentially oviposited on the medium of lowest concentration. In the absence of choice, C. megacephala readily oviposited on fish that had been salted to levels of up to 40% dry weight basis (dwb). Trials investigating the effects of feeding medium salt concentration on larval growth and mortality indicated that a high salt concentration of about 40% (dwb) is necessary to effectively control infestation of salted fish by C. megacephala. Such high salt concentrations are rarely obtained in commercially produced salted dried fish in south-east Asia and would be unlikely to gain consumer acceptance.