nestmates

Nestmates are individuals that belong to the same social unit, such as a colony or nest, within eusocial insects like ants, bees, wasps, and termites. They cooperate in foraging, defense, brood care, and nest maintenance. Nestmate recognition is the process by which colony members identify others as belonging to their own nest and not as outsiders. It is primarily based on cuticular hydrocarbons—hydrocarbon profiles coating the insect's cuticle—that serve as a colony odor. These chemical cues are shared among nestmates through social interactions such as in contact, grooming, and trophallaxis, resulting in a common colony odor. Variation in CHCs can occur with age, caste, diet, or environment, but colonies maintain a stable olfactory signature that outsiders lack.

Non-nestmates are individuals from other colonies or species. When detected, they are typically confronted or attacked to defend resources and brood. Recognition thresholds and learning allow individuals to tolerate familiar neighbors to a degree, a phenomenon known as the dear enemy effect, while maintaining strong defenses against unfamiliar intruders. Some species are subject to social parasitism, where a parasite mimics the host colony's odor to infiltrate nests.

Colony structure influences nestmate recognition. In polygyne colonies with multiple queens, workers may display weaker aggression toward nestmates from the same colony but still distinguish non-nestmates. The study of nestmate recognition informs ecology, evolution, and pest management, and researchers use introduction tests and chemical analyses to explore colony odor and recognition systems.