A Syrphid Fly Uses Olfactory Cues to Find a Non-Yellow Flower
Syrphid flies are frequent flower visitors, but little is known about the cues they use to find flowers. We determined the importance of visual and olfactory cues in a flight cage bioassay using Cirsium arvense (Asteraceae) flower heads and experienced Episyrphus balteatus (Diptera, Syrphidae). We tested the response of antennae of the flies to headspace inflorescence scent samples by using gas chromatography coupled to electroantennography (GC-EAD). The bioassays revealed that both sexes of experienced flies rely on olfactory, not visual, cues to find C. arvense flower heads. The GC-EAD measurements demonstrated that male and female flies have olfactory receptors for several of the compounds emitted by the inflorescences. These electroantennographic-active compounds may be responsible for the attraction of flies to the C. arvense flower heads. Among the compounds eliciting an antennal response are methyl salicylate and 2-phenylethanol, which were previously described as syrphid attractants. Overall, our study demonstrates for the first time that a syrphid fly uses olfactory and not visual cues to find a pollen/nectar host-plant.
KeywordsFloral attraction Olfactory cues Visual cues Episyrphus balteatus Cirsium arvense Behavioral assay GC-EAD Asteraceae Diptera
Gregor Aas helped with plant material and provided the greenhouse and Irmgard Schäffler participated in useful discussions. Lynn Amanda Staff, Joseph Woodring, and two anonymous referees gave valuable comments on an earlier version of the manuscript. CP was supported by a grant (AP2006-03067) from Ministerio de Educación y Ciencia-Spain.
- Lunau, K. 1988. Innate and learned behaviour of flower-visiting hoverflies. Flower-dummy experiments with Eristalis pertinax (Scopoli) (Diptera, Syrphidae). Zool. Jb. Physiol. 92:487–499.Google Scholar
- Lunau, K. and Wacht, S. 1994. Optical releasers of the innate proboscis extension in the hoverfly Eristalis tenax L. (Syrphidae, Diptera). J. Comp. Physiol. A 174:575–579.Google Scholar
- Lunau, K., Hofmann, N., and Valentin, S. 2005. Response of the hoverfly species Eristalis tenax towards floral dot guides with colour transition from red to yellow (Diptera: Syrphidae). Entomol. Gen. 27:249–256.Google Scholar
- Shi, J., Luo, Y.-B., Bernhardt, P., Ran, J.-C., Liu, Z.-J., and Zhou, Q. 2009. Pollination by deceit in Paphiopedilum barbigerum (Orchidaceae): a staminoide exploits the innate colour preferences of hoverflies (Syrphidae). Plant Biol. 11:71–28.Google Scholar