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Holes in plastic bags containing wax moth (Galleria mellonella) caterpillars tipped off researchers that the creatures can break down plastic. César Hernández/CSIC

Animal behaviour

This caterpillar can digest plastic

Wax-moth larvae could inspire biotechnological methods for degrading plastic.

Researchers who were using plastic bags to carry caterpillars have discovered that one species can digest polyethylene, a ubiquitous plastic that is one of the toughest to break down.

Wax moth (Galleria mellonella) caterpillars live in beehives, feeding on honey and wax. Paolo Bombelli and Christopher Howe at the University of Cambridge, UK, and Federica Bertocchini at the University of Cantabria in Spain noticed that plastic bags holding the caterpillars quickly developed holes. To investigate, the team observed the caterpillars on polyethylene film in the laboratory, and found that about 100 of them could degrade 92 milligrams of the plastic in around 12 hours — a much higher rate than that achieved by microbes known to break down polyethylene. Homogenized caterpillar cells had the same effect, showing that the creatures are digesting the plastic, not just chewing it.

This ability may help the caterpillars to digest beeswax, which contains compounds that are chemically similar to polyethylene. It’s not clear whether the caterpillars produce their own polyethylene-digesting enzymes or rely on gut microbes to break down the plastic, the authors say.