Its shape and length is determined by local conditions, the most significant of which are Air Movement and Temperature. When the Pheromone Plume comes into contact with another insect of the same species, it will illicit a response. The type of response elicited depends on the type of pheromone. If successful in his search, he will usually exhibit courtship behaviour. Perhaps the two best known classes of insect pheromones are Sex pheromone and Aggregation pheromone.
Sex pheromones act as described above.
Aggregation pheromones are released by both sexes of certain species, and are more general in the effect that they have on the receiver, e.g. cockroaches typically release aggregation pheromones wherever they are, and in particular in and around sources of nutrition. This type of pheromone generally causes clumping and clustering behaviour of individuals. Many Cockroach lures are mixtures of aggregation pheromones from different species. This means that they are attractive to males, females and nymphs of several species of cockroach. Sex pheromones on the other hand are highly specific to species, sex and even stage of life cycle.