Which of the following best describes a pheromone?

The best description of a pheromone is that it is a natural attractant for species. Pheromones are chemical substances produced and released into the environment by animals, particularly insects, that affect the behavior or physiology of others of the same species. They serve various functions, such as attracting mates, marking territory, or signaling alarm. The nature of pheromones as attractants is crucial in pest management, as they can be used in traps or monitoring systems to lure pests, allowing for better control measures.

In contrast, other options do not accurately capture the essence of what a pheromone is. For instance, describing pheromones as a chemical that repels pests is misleading—while some chemicals might repel insects, pheromones specifically serve to attract them. Additionally, they are not a type of insecticide or a component related to pesticide resistance, as they do not function to control pests through toxicity but rather through behavioral modification.