What is the definition of an aggregation pheromone?

An aggregation pheromone is defined as a chemical signal used by insects to attract members of the same species to a specific location. This type of pheromone is crucial in the social behavior of many insect species as it helps facilitate group formation for purposes such as feeding, mating, or protection. By producing such pheromones, insects can congregate in certain areas, which can be beneficial for survival.

The other choices provided do not align with the concept of an aggregation pheromone. For instance, while some pesticides might affect insect behavior, aggregation pheromones themselves are not pesticides. Similarly, methods of pesticide application and forms of chronic toxicity relate to pest control strategies or the impact of chemical substances on living organisms, rather than the chemical communication mechanisms used among insects. Thus, the identification of aggregation pheromones as chemical signals highlights their role in insect ecology and social structures.