REVIEW Eur. J. Entomol. 105: 797–806, 2008 http://www.eje.cz/scripts/viewabstract.php?abstract=1400 ISSN 1210-5759 (print), 1802-8829 (online) Chemical cues mediating aphid location by natural enemies EDUARDO HATANO1, 2, GRIT KUNERT 2, J.P. MICHAUD3 and WOLFGANG W. WEISSER1 1Institute of Ecology, Friedrich-Schiller-University Jena, Dornburger Str. 159, 07745 Jena, Germany; e-mails:
[email protected],
[email protected] 2Max-Planck-Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745 Jena, Germany; e-mail:
[email protected] 3Kansas State University, Agricultural Research Center-Hays, 1232 240th Ave., Hays, KS 67601, USA; e-mail:
[email protected] Key words. Aphid, natural enemies, host selection, semiochemicals, infochemical Abstract. There is increasing evidence that chemical cues play a pivotal role in host selection by the natural enemies of aphids. We use Vinson’s (1976) division of the host selection process into habitat location, host location and host acceptance for both parasitoids and predators and review what is known about the role of semiochemicals in aphid selection by natural enemies. For habitat location (i.e. detection of the host plant), volatiles emitted by plants after aphid attack have been described for a number of plant-aphid inter- actions. These synomones indicate not only the presence of an aphid host plant to the predator or parasitoid, but also the presence of aphids. Volatiles emitted from undamaged host plants are often attractive to aphid parasitoids, but less so for predators. Host location by the natural enemy on the food plant is guided by semiochemicals that mostly originate from the aphids, in particular aphid alarm pheromone, honeydew, or the smell of the aphid itself.