The persistence of Escherichia coli in the larval gut was examined for both house flies, Musca domestica, (L.) and stable flies, Stomoxys calcitrans, (L.) for up to 48 hours after ingestion. Abundance of E. coli declined over time in immature house flies, but remained constant in immature stable flies, suggesting house fly larvae digest E. coli but stable fly larvae do not. Survival of house fly and stable fly larvae averaged 62% and 25% respectively when reared on pure E. coli cultures. This indicates that house fly larvae use E. coli as a food source while stable fly larvae do not, explaining why E. coli declines in house fly larvae but not in stable fly larvae. Persistence of E. coli throughout the pupal stage and presence in the emerging adult were determined. E. coli load in pupae increased until day three for both species, then decreased significantly one day before emergence of adult house flies, but remained constant until stable fly emergence. E. coli was detected in 78% of emerging house flies and in 28% of emerging stable flies. Over 90% of flies tested were contaminated both externally and internally. The amount of bacteria found on adult flies was correlated with the amount of bacteria found in the empty puparium for house flies but not for stable flies.
Species 1: Diptera Muscidae Musca domestica (house fly)
Species 2: Diptera Muscidae Stomoxys calcitrans (stable fly)
Keywords: bacteria
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