Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2001
Publication Date: N/A
Interpretive Summary: Horn flies and face flies are annoying pests of cattle which lay their eggs in fresh cattle dung where maggots (fly larvae) generally grow quickly, form pupae, and develop into mature adult flies. Efforts to develop methods to control flies that are less dependent on toxic chemical pesticides often require extensive knowledge of pest biology and metabolism. Fly larval development in cattle dung is an attractive target for development of new control technology because fly larvae are dependent on dung for food, and cannot move to a new location to avoid control efforts as easily as adult flies, however, the complex microbial community that thrives in dung often complicates or interferes with studies of fly larval nutrition, metabolism and toxicology. This report identified two methods to deprive fly larvae of needed nutrients, allowing future work to identify what nutrients are necessary. The work also indicated that it is necessary to develop a test to determine whether a substance acts as a feeding stimulant or a feeding inhibitor or deterrent. Information of this type may allow manipulation of fly larval feeding and growth rate, which is important to developing an artificial diet that does not interfere with research studies, or potentially to use as a fly control method by preventing them from feeding normally, and causing their growth to be stunted. Results of this study demonstrated that smaller fly larvae have a reduced chance of developing into adults. It was previously known that small adults have reduced reproductive capacity, suggesting that development of new control technology reducing the growth of larval flies will impact fly populations by reducing the survival rate to form adults which also produce fewer offspring.
Technical Abstract: Aging of bovine dung for 3-5 years under refrigeration depletes nutrients required for growth and development of horn fly larvae. Growth of horn fly larvae in mixtures of nutrient-depleted dung and fresh dung results in production of larvae and pupae stunted in proportion to the relative amount aged dung. Size reduction of pupae produced in aged dung was due to nutrie elimitation which could be reversed by supplementation with a larval extrac Similar stunting of horn fly larval growth and development was produced by larval crowding in fresh bovine dung. Stunting was dependent on degree of larval crowding, with higher larval densities producing decreased size of individuals, but higher aggregate pupal weight, suggesting that stunting at high larval density resulted from phagoinhibition rather than nutrient depletion of the fresh dung. The lower size limit for pupae which are successful in eclosion of adult flies appeared to be about 1.0 mg, compared dan average weight for normal horn flies of about 4.2 mg. Successful eclos of adult horn flies was strongly dependent on pupal size between 1.0 and 2. mg (0.9578 correlation).