One of the signs of cockroach infection is through odor. Odor is usually described as mildew and greasy. This odor is caused by pheromones produced by cockroaches. Pheromones are chemical signals that serve two purposes as a form of communication between cockroaches:
(i) Aggregated pheromones
Although cockroaches are a group life, unlike termite groups, which have an organized social structure, different members play different roles. Cockroaches do not have an organized social structure, they prefer group life. Therefore, when a cockroach finds a good place to live, it indicates that it has the odor of pheromones to attract others.
(ii) Attraction to partners
Pheromones are also used to attract males to mate. Female cockroaches emit pheromones that attract groups of male cockroaches. Humans can smell these pheromones, but for us, it's just a nasty smell. Dead cockroaches also emit another odor called the stench of death. The stench of death is due to oleic acid produced by the carcass of cockroaches. This odor can be used as a warning signal to other cockroaches, indicating that there is a death threat around the area.