These Caterpillars Chow Down on Plastic Bags

César Hernández/CSIC
César Hernández/CSIC / César Hernández/CSIC

Remember The Very Hungry Caterpillar? He may have some serious real-life competition because scientists have discovered that a common caterpillar can eat and digest plastic. They published their findings in the journal Current Biology.

The wax worm is the larval form of the parasitic wax moth (Galleria mellonella), also known as the honeycomb moth. Adult moths chew their way into beehives, then lay their eggs, which will gorge themselves on honeycomb once they hatch. Because bees didn’t already have enough to deal with.

César Hernández/CSIC

Federica Bertocchini is a research fellow at the Institute of Biomedicine and Biotechnology of Cantabria in Spain. In her free time, she’s an amateur beekeeper. One day, she picked handfuls of yellow wax worms out of her hives and tossed them into plastic bags, destined for the trash. But a few hours later, the bags were riddled with holes. The prisoners had made a wiggly break for it.

Bertocchini was intrigued. She and her colleagues rounded up hundreds of wax worms and a bunch of shopping bags and put them all together. The larvae did not disappoint; one 100-worm test group perforated a plastic bag in 40 minutes. Left to their own bitey devices, the caterpillars ate through 92 milligrams of plastic, or three percent of a bag, in a half-day. At that rate, it would take them 17 days to make one bag disappear, which is substantially better than the 100 years it would take otherwise.

Anybody can eat plastic, but whether the worms were actually digesting it is another story. To find out, the researchers killed the larva, mashed them up into a paste, and smeared it on plastic film. Just 14 hours later, the caterpillar jam had eaten through 13 percent of the plastic.

Many questions remain. For starters, what exactly is digesting the shopping bags? It’s not clear if the ability to break down the plastic is inherent to the caterpillars, like a digestive enzyme, or if their guts are home to plastic-eating bacteria.

"If a single enzyme is responsible for this chemical process,” first author Paolo Bombelli of Cambridge said in a statement, “its reproduction on a large scale using biotechnological methods should be achievable. This discovery could be an important tool for helping to get rid of the polyethylene plastic waste accumulated in landfill sites and oceans.”

The researchers also noted that the caterpillars cannot live on shopping bags alone. “These animals don’t live on plastic,” Bertocchini told New Scientist. “They eat it to get out of it, or get to the food behind it. If in the future something evolves to exclusively eat plastic, I don’t know. So far it hasn’t happened.”