Semochemicals

Semochemicals are signaling chemicals produced by organisms to affect the behavior or physiology of other organisms. The term covers a broad class of compounds used in chemical communication, from insect mating signals to plant-derived cues that influence herbivores and their natural enemies. The study of semochemicals falls under chemical ecology and involves understanding how these signals are produced, released, detected, and interpreted in ecological contexts.

Semochemicals are divided into pheromones, which mediate communication within the same species, and allelochemicals, which mediate interactions between different species. Allelochemicals are further categorized as kairomones, allomones, and synomones, depending on which party benefits from the signal: kairomones benefit the receiver, allomones benefit the sender, and synomones confer advantages to both.

Examples include pheromones that guide insects to mates (sex pheromones) or establish trails (trail pheromones in social insects), and alarm pheromones that trigger defense responses. Plants emit volatile semochemicals when damaged by herbivores, which can attract predators or parasitoids of the herbivores, or influence pollinator behavior. These signals can operate over short or long distances and can be degraded by environmental conditions.

Applications include pest management through pheromone traps and mating disruption, as well as the use of attractants and signals to study ecological relationships. Analytical approaches such as gas chromatography–mass spectrometry and electroantennography are commonly used to identify and characterize semochemicals.