House flies and pig manure volatiles: Wind tunnel behavioral studies and electrophysiological evaluations

Nine compounds from the headspace of fresh pig manure were identified as electrophysiologically active on virgin female house fly (Musca domestica L.) antennae, and mixtures of these compounds attracted female house flies in wind-tunnel behavioral assays. Identification was accomplished by using coupled gas chromatographic-electroantennographic (GC-EAG) recordings, coupled gas chromatographic-mass spectrometric (GC-MS) analysis, electroantennographic (EAG) assays of standards, and wind tunnel behavioral studies. The pig manure volatiles eliciting responses from female antennae were butanoic acid, 3-methylbutanoic acid, dimethyldisulfide, dimethyltrisulfide, dimethyltetrasulfide, phenol, benzeneethanol, indole, and 3-methylindole. In EAG dose-response tests butanoic acid, 3-methylbutanoic acid, indole, and 3-methylindole elicited the highest responses on female house fly antennae, and dimethyltrisulfide, phenol, and benzeneethanol elicited more moderate responses. In wind-tunnel behavioral studies, female house flies flew upwind in the plume and landed on the source in response to pig manure volatiles. The ability of individual EAG-active compounds to attract female house flies was not significantly greater than that of the control. However, two mixtures, one comprised of seven EAG-active compounds and a second made up of only three compounds, were capable of attracting female flies in a similar manner as found with pig manure. The behavioral significance of these compounds as potential attractants is discussed.