The Chemical Ecology of Aphids

Insects are sensitive to chemical aspects of their environment, particularly with regard to host and mate location. Aphids can select individual or a few closely related host plant species from a wide range of nonhost vegetation (65, 71). This selection relies upon the detection of secondary plant compounds as well as primary metabolites associated with the physiological condition of the host plant (82). Use of long-range volatile chemical cues in aphid-plant and aphid-aphid interactions was formerly considered unlikely (78, 108). Never­ theless, recent work reviewed here demonstrates that olfaction plays a more extensive role in the chemical ecology of aphids than previously thought. Thc study of aphid chemical ecology involving volatile semiochemicals, particularly pheromones, has been greatly enhanced by the development of electrophysiological rccordings from aphid antennae, using the electroan­ tennograph (EAG) and single-cell recording (SCR) methods. SCR directly coupled to high-resolution capillary column gas chromatography (GC-SCR) provides a powerful tool for locating the active components in behaviorally active samples (154). Analysis by other highly sensitive techniques such as