Inter‐kingdom signaling — symbiotic yeasts produce semiochemicals that attract their yellowjacket hosts.

In recent studies, the yeast species Hanseniaspora uvarum and Lachancea thermotolerans were isolated from the digestive tract of four North American yellowjacket species (Hymenoptera: Vespidae), and attraction of yellowjackets to brewer's yeast, Saccharomyces cerevisiae (all Saccharomycetaceae), growing on fruit powder was demonstrated. We tested the hypothesis that Vespula spp. are attracted to cultures of H. uvarum and L. thermotolerans and their respective volatiles. In field experiments, we found that H. uvarum and L. thermotolerans are attractive to three species of yellowjacket, but only when grown on grape juice‐infused yeast peptone dextrose (YPD) agar. Using gas chromatography‐mass spectrometry, we analyzed the headspace volatiles produced by these yeasts, and field tested an 18‐component yeast synthetic semiochemical blend. This synthetic blend attracted western yellowjackets, Vespula pensylvanica (Saussure), but no other yellowjacket species. Acetic acid or ethanol added to the synthetic blend at biologically relevant doses either had no effect or significantly lowered trap captures. Our results demonstrate that yeast symbionts isolated from the digestive tract of yellowjackets are attractive to their hosts. Further research is needed to identify the volatiles mediating attraction of species other than V. pensylvanica to the yeast cultures. Yellowjackets in the genus Vespula (Hymenoptera: Vespidae) harbor the yeasts Hanseniaspora uvarum and Lachancea thermotolerans (both Saccharomycetaceae) in their digestive tract. Our research demonstrates that yellowjackets are attracted to these yeasts growing on grape juice‐infused agar, and a synthetic blend of 18 volatiles produced by the yeasts is attractive to western yellowjackets, Vespula pensylvanica. The volatiles produced by symbiotic yeasts show potential for use as a yellowjacket trap bait. [ABSTRACT FROM AUTHOR]