Feces in termites’ nests block biological pest control

Mixing their own poop into nest walls gives Formosan termites a bacterial boost in fighting off human attempts to destroy them with insect plagues.

A bacterial strain found in the fecally-enhanced nest walls of pest termites Coptotermes formosanus helps protect them from a potentially deadly fungus, says entomologist Nan-Yao Su of the University of Florida in Fort Lauderdale. Such live-in boosters could help explain why efforts to control the termites with fungal diseases have been a failure, Su and his colleagues report September 18 in the Proceedings of the Royal Society B.

“You can put the fungus on an insect in a lab dish and say, ‘Hah! We killed the termite,’” Su says. But for termites in their natural colonies, the soil-dwelling fungus Metarhizium anisopliae has failed to devastate.

Meanwhile Formosan termites are destroying homes, railroad ties and even living trees. Colonies of these termites have proven among the pests most destructive to wood in the southeastern United States and Hawaii. A subtropical species from Asia, it turned up in Texas in 1951. A single colony can grow to more than a million termites scurrying through multiple underground nests and a tunnel network ranging across 150 meters.

After millions of years of crowding into warm, humid nests underground, the termites have evolved both biology and behavior that can fight fungi, says coauthor Thomas Chouvenc, also at the University of Florida. Termites attend to personal hygiene and invite grooming by stretching out a leg or exposing a body area. Nest mates oblige by nipping off detritus, which passes into the formidable termite gut, where pathogens typically die. The new study, Chouvenc explains, explores how termites export their gut’s protective power to the walls of their nests.

Formosan termites create a fecal lining for their foraging tunnels and mix feces with chewed plant material to make the structural material for the rest of their homes.

Earlier work from other labs had suggested that the termites excrete pathogen-combating bacteria.

Microbiologist and coauthor Monica Elliott, also at the University of Florida, worked with the entomologists to isolate more than 500 Actinobacteria strains from structural material in five termite nests. (Actinobacteria are common microbes in soil.) Researchers used tests in lab dishes to screen the bacteria for pathogen-fighting ability. They used a representative fighter in more naturalistic experiments: Termites were tucked into sand and sterilized structural material between planes of Plexiglas. Letting one strain of the Actinobacteria, a kind of Streptomyces, establish itself in the sand allowed 1.6 times as many termites to survive 60 days of fungal contamination when compared with bacteria-free sand.

What’s most interesting to urban entomologist Gregg Henderson of Louisiana State University in Baton Rouge is that Chouvenc and Su have declared human termite science a 50-year failure at biological control yet “show how simply and elegantly it is performed by the termites themselves.”