Growth and survival of immature Haematobia irritans (Diptera : Muscidae) is influenced by bacteria isolated from cattle manure and conspecific larvae

Twenty species of bacteria were isolated from cattle manure and seven speci es were isolated from the gut of larval horn fly Hematobia irritans (L.). B acteria in manure belonged to the Bacillaceae, Pseudomonadaceae, Micrococca ceae, Corynebacteriaceae, Enterobacteriaceae, Microbacteriaceae, and two un assigned genera. Gut bacteria belonged to the Enterobacteriaceae, Bacillace ae, Neisseriaceae, and Pseudomonadaceae. H. irritans larval survival and gr owth on the various bacterial species were evaluated by rearing larvae in s terilized cattle manure that was inoculated with single bacterial isolates. H, irritans larvae failed to develop in sterilized, uninoculated manure, i ndicating that bacteria are necessary for larval development. Survival aver aged 74% in nonsterilized manure and ranged from 4 to 53% in manure with in dividual isolates. Survival was highest when larvae were reared on manure i noculated with Pseudomonadaceae, Corynebacteriaceae, Micrococcaceae, and Ba cillaceae and was lowest when reared in manure inoculated with Enterobacter iaceae and Microbacteriaceae. Pupal weights were heaviest when reared on th e Flavobacteria, followed by the Pseudomonadaceae and Corynebacteriaceae, P upae averaged 4.9 +/- 0.08 mg when reared on gram-negative isolates, compar ed with 3.6 +/- 0.09 mg when reared on grampositive isolates. Pupal weights were not significantly correlated with larval survival, indicating that ba cteria that promote growth do not necessarily promote survival. A reproduct ive index was used as a measure of fitness and was highest for larvae reare d in the nonsterile control, followed most closely by Pseudomonadaceae and Corynebacteriaceae. These groups appeared to Lest meet the nutritional requ irements of larvae and may be used in further experiments to define an arti ficial rearing media for H. irritans.