_____ are chemical signals that, instead of being secreted into the bloodstream, are introduced by animals into their habitats. they can be used to attract mates and mark territories.
Pheromones is your answer. Pheromones are hormones that can act outside of the body - they they are mostly used by humans and insects in order to attract mates. There are several different pheromones, in fact, that have an effect on behavior.
