Aggregations of the red and black coloured firebugs are ubiquitous under linden trees in Central Europe, where the bugs can reach astounding population densities. While these insects have no impact on humans, their African, Asian, and American relatives, the cotton stainers, are serious agricultural pests of cotton and other Malvaceous plants. Researchers at the Max Planck Institute for Chemical Ecology in Jena, Germany, recently discovered that these bugs need bacterial symbionts to survive on cotton seeds as their sole food source.
By using high-throughput sequencing technologies, they found out that firebugs and cotton stainers share a characteristic bacterial community that colonizes a specific region of their mid-gut. Removal of the symbionts or reciprocal exchange of bacteria between firebugs and cotton stainers led to high mortality and low mating success, demonstrating the importance of the bacterial helpers for growth and reproduction. Thus, symbiotic bacteria constitute a key factor not only for the ecological success of firebugs but also for the pest status of cotton strainers.
With more than 80,000 described species, the true bugs represent one of the five megadiverse insect orders on earth. Many species are serious agricultural pests that are responsible for significant losses in crop production. Among these are cotton stainers, bugs of the family Pyrrhocoridae that damage cotton by feeding on the seed bolls and leaving indelible stains in the harvested crop. While previous research on sap-sucking insects demonstrated that they rely on microbial symbionts for nutrition, it remained unknown how cotton stainers and other seed-feeding bugs exploit Malvaceous plant seeds that are rich in toxic secondary metabolites, but poor in some essential nutrients.