Scientists have discovered that the cockroach diet has impact on the way the insects come together in groups.
It has long been recognised that cockroaches use an aggregation pheromone to facilitate attraction, which results in cockroaches coming together in loose social groups in harbourages.
However, the aggregation pheromone is not one chemical and not even produced by the cockroach itself, but is rather the result of metabolites produced by the gut microbes. But given that the microbial community is influenced by diet and that the diet will also influence the metabolites, the question is, how do the gut microbe metabolites create a reliable aggregation pheromone? Recent research has taken a closer look at these cockroach aggregation pheromones.
Newly hatched German cockroach nymphs do not have gut microbes – they build up the necessary gut microbial community through eating the faeces of nestmates (coprophagy). The makeup of the gut microbe community is also influenced by diet. Researchers have carried out a series of trials, feeding cockroach nymphs the faeces from adult cockroaches that had been fed on different diets (cat food, rodent food and rabbit food), and seeing which faeces the nymphs prefer.
Naïve nymphs that had not been fed any faeces showed no preference between the faeces from cockroaches on the different diets. They were equally attracted to all faeces, showing an innate attraction to faeces. However, experienced nymphs that had been fed the faeces of adults on only one specific diet preferred these faeces to faeces from adults on a different diet. Furthermore, when naïve nymphs were also fed glucose then fed faeces from adults on one specific diet, they subsequently preferred those faeces over the faeces from cockroaches on a different diet.
These observations allowed the authors to propose that the aggregation pheromone of the German cockroach is not a single chemical or group of chemicals but rather consists of two general classes of faecal odours. One class consists of chemicals that stimulate innate odour preferences, and the second class consists of faecal odours specific to the local population, which are based largely on diet. It is this attraction to the second class of odours that is learnt through coprophagy soon after hatching. By maintaining a strong attraction to the local cockroach population, newly hatched cockroaches acquire a gut microbial community adapted to the likely diet in the environment.
From a cockroach control point of view, the authors believe this study highlights two phenomenon that could impact the development of control techniques. Firstly, it demonstrates that cockroaches are able to learn – which means they can learn to accept or avoid a food or odour. Secondly, by understanding the nature of the aggregation pheromone, focusing on research to understand the innate aspect of the attraction could help identify chemicals for use in traps and baits.
Further reading: Wada-Katsumata, Q et al. (2026). Group recognition in the German cockroach, a subsocial omnivore, is based on faecal odour preference that is modulated by coprophagy, diet and learning. Proc. R. Soc. B (2026) 293 (2076): 20253042. https://doi.org/10.1098/rspb.2025.3042
