Allelochemicals can be further subdivided into three groups based on who “benefits” from the message:
- Allomones benefit the sender — such as a repellent, or defensive compound (e. g. cyanide) that deters predation.
- Kairomones benefit the receiver — such as an odor that a parasite uses to find its host.
- Synomones benefit both sender and receiver — such as plant volatiles that attract insect pollinators.
Insects use their sense of taste or smell to detect the presence of semiochemicals. Specialized receptors may be located anywhere on the body, but are especially common on the feet, antennae, palps, and ovipositor (see Chemoreceptors). The sense of smell (olfaction) is used for remote chemoreception — detecting semiochemicals with low molecular weight that are volatile enough to become airborne. The sense of taste (gustation) is used for contact chemoreception — detecting molecules that adhere to a substrate or to the outside of an insect’s body.