Dynamics of growth modified by larval population density in the flesh fly, Sarcophaga bullata

Abstract

Growth functions were fitted to the growth curves of larvae of the flesh fly, Sarcophaga bullata Parker (Diptera: Sarcophagidae), reared in conditions that were either uncrowded (25 larvae per 25 g beef liver) or crowded (400 larvae per 25 g beef liver). The growth curves took the form of logistic functions that were symmetrical for uncrowded larvae, but asymmetrical for crowded ones. Initially, crowded larvae grow faster than uncrowded larvae, a response in contrast with those of all other species of higher Diptera studied to date. Apparently, crowded larvae derived benefit from close intraspecific associations, for their rapid growth took place while they fed within dense aggregations. The growth rate of crowded larvae peaked early and growth ceased abruptly when the supply of food was exhausted. Their feeding period was reduced by 60% and their weight by 74% in comparison with those of uncrowded larvae.