Biology of Chrysomya megacephala (Diptera: Calliphoridae) and reduction of losses caused to the salted-dried fish industry in south-east Asia

Abstract

AbstractChrysomya megacephala (Fabricius) is shown to be a principal cause of loss of salted-dried fish in south-east Asia. Field and laboratory work conducted in 1982–1989 was aimed at reducing these losses. Field work at a small–scale fish processing site in Cirebon, West Java, showed that fully gravid C. megacephala females were highly differentially attracted to fish at the salting stage, which means that the salting tanks must have properly designed fly-tight lids to prevent infestation. C. megacephala counts and ovary examinations showed that females with various stages of immature ovaries (stages I–IV) were predominent during the drying stage after the fish had been removed from the salting tanks, with numbers usually greater on the first day of drying than the second. C. megacephala counts were high during the dry season, although numbers fluctuated enormously depending on weather, among other factors. Physically screening fish during the initial drying period effectively controlled infestation, although problems associated with the screen design were identified. In laboratory cultures adult sex ratio was approximately 1:1 and longevity in both sexes, over three generations, ranged from 47 to 55 days (maximum induced longevity, 98 days) at c. 29°C, 30–60% r.h.; under similar conditions, 10% of females had mature (stage V/VI) oocytes after one week, 40% after two weeks and 90% after three weeks. Mean number of ripe oocytes in gravid flies was 221 (range 151–228).