Sensory and behavioural responses of the stable fly <i>Stomoxys calcitrans</i> to rumen volatiles

Analysis of volatiles from rumen digesta by gas chromatography linked antennogram recordings from <i>Stomoxys calcitrans</i> (L) (Diptera: Muscidae) antennal receptor cells revealed about 30 electrophysiologically active constituents, the most important of which is dimethyl trisulphide with a sensory threshold in the femtogram range. The behavioural responses of <i>S. calcitrans</i> to five chemostimulants (dimethyl trisulphide, butanoic acid, <i>p</i>-cresol, oct-1-en-3-ol and skatole) were tested in a wind tunnel where activation and attraction of hungry flies to rumen volatiles were recorded. Dimethyl trisulphide, butanoic acid and <i>p</i>-cresol were found to attract <i>S. calcitrans</i>. This sensitivity to rumen volatile constituents, that also occur in animal wastes used for oviposition by <i>Stomoxys</i> spp., as well as in flowers used by stable flies as sources of nectar is discussed in the context of the behavioural ecology of these flies.