New Cockroach Deterrents Possible Thanks to Chromatography and Faeces

We’ve all heard the unnerving story that cockroaches can survive a nuclear holocaust — but can they communicate with each other? If so, how? It’s fairly common to see large groups of the little critters congregating together – how do they know where to go? Is there a memo sent round?

The answer is actually far more simple and disgusting. New research undertaken using gas chromatography in conjunction with mass spectrometry (GC-MS) concluded that certain pheromones present in the faeces of cockroaches send out signals to their fellow beasties, attracting them to their location.

Such knowledge of their communication and attraction methods may allow scientists to develop more effective attractants and deterrents, leading to better baits, traps and repellents.

A gut feeling

A team of scientists from North Carolina State University studied the faeces of cockroaches and found that bacteria in their guts created a number of different fatty acids. These acids in the production of certain pheromones which manifested themselves in the faecal excretions of the roaches. These pheromones then served as a sort of attraction beacon, inviting other roaches to aggregate.

The key pheromones were pinpointed by comparing analyses of faeces of roaches with and without the gut bacteria. In those that did not have the bacteria present — the faeces were found to contain only miniscule traces of 24 chemical compounds found in much greater abundance in those roaches with the bacteria. Even more instructive, there were a further 12 compounds that were completely absent altogether.

The researchers then tested the two sets of faecal substances on cockroaches of all ages and found that they gathered in much greater numbers when the compounds were present – especially if they were still nymphs (new-born cockroaches). This happened both when the roaches were tested in groups or individually, showing the conclusiveness of the study.

“The chemical compounds seem especially essential for nymphs,” explained Ayako Wada-Katsumata, lead author on the project. “It's important for nymphs to determine a safe place, and these pheromones help do just that.”

Developing new traps

Once we are able to understand how and why cockroaches congregate, we can set about replicating similar pheromones artificially in order to draw the unwanted creatures into traps. Therefore, such work is key in developing new strategies of curbing cockroach populations, which can run rampant in certain parts of the world.

It’s not the first time that GC-MS has been used to discover how insects interact with each other. The technique is suitable for such studies due to its precision and ability to identify individual components of a substance — allowing scientists to pinpoint exactly what the pheromones in question are. The optimisation of a GC method is discussed in the article, Optimisation of Column Parameters in GC.

Hopefully, further study will allow researchers to develop effective repellents and traps — without the use of pesticides that can be harmful to other species and the environment.

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