Sex pheromone

The many types of pheromones (i.e. alarm, aggregation, defense, sexual attraction) all have a common cause acting as chemical cues to trigger a response.

They meet the criteria for such ornaments that Charles Darwin set out in The Descent of Man, and Selection in Relation to Sex.

[5] In oriental beetles (Exomala Orientalis), females release the pheromone and passively wait for a male to find them.

[4] It is likely that most externally fertilizing species (e.g. marine worms, sea urchins) coordinate their sexual behaviour (release of sperm and eggs) using pheromones.

[9][10] While humans are highly dependent upon visual cues, when in close proximity, smells also play a role in sociosexual behaviors.

It is detected in the antennae of the male moth by a pheromone-binding protein which carries the bombykol to a receptor bound to the membrane of a nerve cell.

[14] It is one of the most potent known biological effector molecules, as it can trigger sexual development at a concentration as low as 10−16 moles per litre.

For monitoring, pheromone traps are used to attract and catch a sample of pest insects to determine whether control measures are needed.

This can be either by releasing enough pheromone to prevent males from finding females, effectively drowning out their signals, or by mass trapping, attracting and removing pests directly.