Mediation of host selection by cuticular hydrocarbons in the honeybee tracheal MiteAcarapis woodi (Rennie)

Using a simple two-choice bioassay and video analysis of individual locomotory tracks, it was determined that a preference for young-bee hosts over old-bee hosts in female honeybee tracheal mites,Acarapis woodi (Rennie), is chemically mediated. When presented with a choice of cuticular extracts from 5-day-old and <1-day-old adult bees, mites showed a significant preference for the young-bee extract in three of four bee colony sources. This discrimination was due apparently to a greater positive response elicited by the young-bee extract rather than a deterrent effect of old-bee extract, as the extract of old bees evoked a significantly higher response than a hexane control. A bioassay of silica-gel fractions of young-bee extract indicated that cuticular hydrocarbons alone were responsible for tracheal mite response. Further fractionation of a hydrocarbon fraction by argentation chromatography demonstrated that both saturated and unsaturated hydrocarbons were involved in the mite response, but when presented in opposition, mites showed a stronger response to the saturated than to the unsaturated components. Mites placed in zones treated with cuticular extract of young bees exhibited higher angular velocities than those placed on hexane, causing them to remain in the extract-treated zones for extended periods. These results point to a possible control strategy whereby migration of tracheal mites to young-bee hosts could be disrupted by artificially altering the chemical profile of the honeybee cuticle.