Carrion beetles of the subfamily Nicrophorinae search and bury a carcass that they utilize for reproduction. After burial, the carcass is coated with oral secretions that delay its decomposition. Previously, oral secretions of Nicrophorus marginatus were found to show antimicrobial activity, whereas secretion of N. carolinus lacked significant activity. Here, we tested the effects of temperature, sex of the beetle, and food type on the antimicrobial properties of oral secretions of both species. Unlike previous findings, we found that oral secretions of N. carolinus had antimicrobial activity. Temperature had significant effects on the amount of secretion protein. When protein concentrations were standardized to 1 micro/ml, N. marginatus secretions had higher antimicrobial activity at cooler temperatures, while N. carolinus had higher activity at warmer ones. The sex of the beetle did not affect antimicrobial activity for either species. Beetles of both species that were fed whole rats contained more protein in their oral secretions than beetles fed with equally sized pieces of raw ground beef. After standardizing the resulting protein concentrations to 1 microg/ml, antimicrobial activity of oral secretion increased for N. carolinus after rat feeding, but not for N. marginatus. Our results highlight key ecological differences between these closely related species. In addition, they demonstrate the importance of experiments being conducted under varying environmental conditions when evaluating species for potential antimicrobial compounds.

Flies are known to be mechanical vectors of bacterial, viral, and parasitic diseases. Although flies are known to transmit disease, the effects of cleaning behavior have not been well studied. This study quantified the cleaning effectiveness and behavior of three fly species: Sarcophaga bullata, Musca domestica L., and Drosophila virilis. Flies were transferred to plates of Escherichia coli or Pseudomonas aeruginosa and allowed to walk on the bacteria for a total of 5 min. After the flies were contaminated, they were either immediately collected to quantify bacteria or were placed onto sterile plates to clean for 5 or 10 min. After cleaning, flies were placed into tubes with 1 ml of sterile 0.85% saline and were gently shaken for 1 min to remove bacteria. A serial dilution was made and 50-µl spot titers were plated. Cleaning behavior was also monitored and scored for a period of 5 min. Results demonstrate a bacterial reduction for both bacteria on all three fly species. Sarcophaga bullata and D. virilis both showed a significant reduction of both bacteria within 10 min, whereas M. domestica only showed a significant reduction in P. aeruginosa. Cleaning behavior increased significantly in flies that were exposed to bacteria compared to flies that were not exposed to bacteria. This study is important, as it demonstrates that fly cleaning could affect mechanical transmission of disease, and additional studies should look at flies' abilities to remove other types of microorganisms.