Caterpillars cultivate a diverse community of digestive bacteria that process the plastic, researchers said.
Dousing old plastic in a similar mix of bacteria might speed the breakdown of the persistent pollutants, they said.
According to Anisha Navlekar of Texas Tech University in the US, some bacteria have been shown to colonise and help degrade plastics in the ocean, so it makes sense that the microorganisms also appear to be helping the caterpillars break down plastics.
Polyethylene is widely used to make plastic bags and other packaging materials, but it hangs around in landfills for decades, perhaps even centuries, 'Science News' reported.
More From This Section
Caterpillars that ate a control diet of bran and wheat had guts mostly dominated by Turicibacter, a group of bacteria commonly found in animals' digestive tracts, said Navlekar.
However, the caterpillars that munched on the plastic had a much more diverse native microbial community.
In particular, they had high levels of a few types of bacteria: Tepidimonas, Pseudomonas, Rhizobiales and Methylobacteriaceae.