Meet the “plastivore” caterpillars that grow fat from eating plastic

(Press-News.org) Plastics play a fundamental role in modern life, but their resistance to biodegradation makes them very difficult to dispose of. New research reveals how “plastivore” caterpillars can metabolically degrade plastics in a matter of days, not decades, and store them internally as body fat – but at what cost?

In 2017, a groundbreaking study demonstrated that the caterpillars of the greater wax moth (Galleria mellonella), known as waxworms, can degrade polyethylene plastic. Polyethylene is the world’s most commonly manufactured plastic, with over 100 million tonnes of polyethylene produced globally each year. Polyethylene is chemically resilient, which makes it resistant to decomposition and can take decades or even hundreds of years to fully degrade.

While this plastic degradation process has been demonstrated by waxworms at a small scale, this ongoing research project is helping us to better understand the biological mechanisms at work, the impact of an all-plastic diet on the health of these organisms, and their viability as a sustainable solution to plastic pollution.

“Around 2,000 waxworms can break down an entire polyethylene bag in as little as 24 hours, although we believe that co-supplementation with feeding stimulants like sugars can reduce the number of worms considerably,” says Dr Bryan Cassone, a Professor of Insect Pest and Vector Biology in the Department of Biology at Brandon University, Canada. “However, understanding the biological mechanisms and consequences on fitness associated with plastic biodegradation is key to using waxworms for large-scale plastic remediation.”

Utilising a suite of techniques spanning animal physiology, material science, molecular biology and genomics, Dr Cassone and his team have studied the interesting relationship between waxworms, their bacterial microbiome, and their potential for large-scale plastic biodegradation, as well as the possible impacts on waxworm health and survivability.

This research reveals that waxworms metabolically process the plastics down into lipids and store it as body fat. “This is similar to us eating steak – if we consume too much saturated and unsaturated fat, it becomes stored in adipose tissue as lipid reserves, rather than being used as energy,” says Dr Cassone.

While waxworms will readily consume polyethylene, this research also shows that this ultimately ends in a quick death. “They do not survive more than a few days on a plastic-only diet and they lose considerable mass,” says Dr Cassone. “However, we are optimistic that we can formulate a co-supplementation that not only restores their fitness to natural levels but exceeds it.”

Dr Cassone and his team have identified two ways in which waxworms could contribute solutions to the ongoing plastic pollution crisis. “Firstly, we could mass rear waxworms on a co-supplemented polyethylene diet as part of a circular economy,” he says. “Secondly, we could explore the re-engineering of the plastic biodegradation pathway outside the animal.”

As a bonus benefit, the mass production of waxworms would also generate a substantial surplus of insect biomass, which could represent an additional economic opportunity in aquaculture. “Our preliminary data suggests that they could become part of a very nutritious diet for commercial food fishes,” says Dr Cassone.

This research is being presented at the Society for Experimental Biology Annual Conference in Antwerp, Belgium on the 8th July 2025.

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