Volatile soil molecules entice ants to nest

Realtors know that the smell of freshly baked cookies may entice humans to buy a house, but to red fire ants geosmin smells like home. A research team led by Daifeng Cheng, an entomologist at the South China Agricultural University, has shown that Solenopsis invicta prefer to nest in soil that gives off the fragrance of actinobacteria—namely geosmin and 2-methylisoborneol (PLoS Pathog. 2020, DOI: 10.1371/journal.ppat.1008800). That’s because actinobacteria in S. invicta nest sites help protect the ants from infectious microbes such as fungi. The researchers showed that newly mated queens are attracted to the odor of these volatile molecules, which are released from soil rich in actinobacteria—specifically Streptomyces and Nocardiopsis—and low in pathogenic fungi. As a result, the microbial perfume indicates to the queens that the soil is a safe place to start a new colony. The team went on to show that the S. invicta queens that nested in such sites were more likely to survive than queens that nested in soil without actinobacteria. This is the first study to show that chemical signals from bacteria can affect the nesting behavior of ants, Cheng says. Now his team aims to determine if these chemical signals can be leveraged to manage S. invicta infestations in public parks and crop fields.