Final answer:
A moth can determine the direction of pheromones by sensing the concentration gradient through its antennae, which are highly sensitive to these chemical signals. This enables them to locate the source, typically for mating purposes.
Step-by-step explanation:
When a moth detects pheromones, it can determine the direction they are coming from by sensing the difference in concentration of these chemical signals. Male moths are equipped with highly sensitive antennae that can detect female pheromones over large distances. Upon perceiving pheromones, which are chemical signals used by moths to communicate, moths can move in the direction where these signals are more concentrated, and through this gradient, find their way towards the source, typically a female moth emitting the pheromones for mating.
The sensitivity of moth antennae is so acute that some species are capable of responding to very low concentrations of specific substances, even detecting them from several miles away. Pheromones play a significant role in a variety of behaviors including mating, where males are attracted to the odours released by females, which guides them to their potential mates. This chemosensory process is crucial for the survival and reproduction of moth species and is found in a variety of other organisms, which use pheromones for communication purposes as well.