Newborn German cockroaches use pheromones in cockroach feces to identify members of their own colony and form a kind of social bond, a discovery which could be used to improve pest control efforts.

Scientists compared neonate cockroaches that had been allowed to consume their colony’s feces and were exposed to fecal odors to neonates that had not engaged in coprophagy. German cockroaches are born with no gut microbiome, and rely on eating feces from a collective fecal pile within their cockroach “aggregation” to gain the microbes and fecal nutrients they need.

Neonates who ate from the aggregation’s feces after hatching displayed an affinity for the specific pheromone present in that aggregate, while the neonates without any microbiome – known as naïve neonates – showed a much broader and less focused array of interests.

“This finding could be used to help control cockroach infestations,” said Ayako Wada-Katsumata, lead author of the paper and a principal research scholar in North Carolina State University’s Department of Entomology and Plant Pathology.

“What we’ve found is that aggregation pheromones are extremely important in how these cockroaches find each other and group together,” says Wada-Katsumata. “Because the aggregation gives these neonates everything they need early in life, they have little reason to leave it, which makes traps and insecticidal baits less effective.

“If we can develop an aggregation pheromone that works across the entire species, we could make traps and baits far more effective and make it easier to control populations in places like residences, hospitals, and restaurants.”

Beyond the practical applications, this research also unveils a fundamental misunderstanding about cockroach social structures, said Coby Schal, co-author of the paper and the Blanton J. Whitmire Distinguished Professor of Entomology at NC State.

“We think of cockroaches as being subsocial, in that they are not completely solitary but also do not exhibit the kinds of group behaviors that bees or ants do,” Schal said. “The use of fecal aggregation pheromones to recognize their natal group is a behavior that mirrors that of social insects like bees, wasps, ants and termites, which typically use body odors instead of fecal odors to recognize nest-mates. Both groups of insects share a similar mechanism that involves learning and memory of their colony’s unique odor, but the anatomical source of the pheromone is different.”

This behavior implies a greater capacity for social structure and learning than has often been attributed to the German cockroach, Schal said.

“What we’re seeing here is a capacity for learning and memory retention that is often thought of as being above an insect as primitive as the cockroach,” he said. “Cockroaches have evolved their own twist on forming kin bonds.”

The paper, “Group recognition in the German cockroach, a subsocial omnivore, is based on faecal odour preference that is modulated by coprophagy, diet and learning,” is published in Proceedings B. Co-authors include Jamora A. Hamilton-Brown and Madhavi L. Kakumanu of NC State University.

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