The very hungry caterpillars

hungry caterpillars

Scoring runner up prize in UNSW’s Bragg Writing Prize is Ebony Wallin’s essay about the very hungry caterpillars that can digest plastic. Ebony’s essay investigates the exciting possibilities of this new discovery, and what it means for the future of our planet. Read Ebony’s essay below.


The Very Hungry Caterpillars

Planet Earth is being contaminated by plastic.  Plastic is a substance of incredible durability, thought to be unable to biodegrade, and immune to anything nature could throw at it.  However, nobody had considered the caterpillars.

Dr. Federica Bertocchini, a Spanish biologist, discovered an extraordinary ability of the waxworm caterpillar entirely by accident. Dr Bertocchini, an amateur beekeeper, had removed waxworm caterpillars from her beehive where they had been eating the beeswax, and placed them in a plastic bag. To her utmost astonishment, within an hour the polyethylene bag was riddled with holes. Dr Bertocchini, and a few colleagues called to the scene, investigated and found ethylene glycol, a component of polyethylene plastic (PET), in the caterpillars’ guts. This confirmed that these caterpillars are able to digest the plastic, and that a waxworm caterpillar’s digestive system can also chemically transform the plastic into ethylene glycol, a highly useful substance found in items such as antifreeze.

But how is this possible? It may be that the waxworms can digest the polyethylene plastic due to a similarity between the chemical structure of the plastic and the beeswax they eat. Beeswax is composed of many compounds with a variety of different chemical bonds, the most common being the carbon-carbon single bond, which is also found in polyethylene plastic. As Dr Bertocchini notes, “Wax is a polymer, a sort of ‘natural plastic’, and has a chemical structure not dissimilar to polyethylene.” The reason for waxworm caterpillars’ ability to biodegrade polyethylene plastic is likely to lie in the bacterial species in their gut. Two bacterial strains capable of digesting the plastic have already been found.

Dr Bertocchini and her fellow researchers are continuing to explore the molecular details of the degradation process of not only plastic, but beeswax as well. By discovering precisely how the digestive system of the caterpillars biodegrade polyethylene plastic, they intend to replicate the process using biotechnology and use it in the war on plastic. “We are planning to implement this finding into a viable way to get rid of plastic waste, working towards a solution to save our oceans, rivers and all the environment from the unavoidable consequences of plastic accumulation,” says Dr Bertocchini. This new research into how the waxworm caterpillars can digest polyethylene plastic has profound implications for addressing the problem of plastic contamination.

The war against plastic is becoming more difficult by the day and the need for efficient weapons more urgent.  Plastic’s durability is what makes it so useful to humans and so potent to nature. This durability usually ensures it does not biodegrade, rather it continually photodegrades, meaning it breaks into smaller pieces known as nurdles. Plastic often ends up in the oceans, manifesting and covering large swathes of the world’s ocean surfaces. The plastic debris pollutes the oceans and traps, poisons or starves animals who encounter it through entanglement or consumption. Therefore, the discovery that a common caterpillar can eat polyethylene, one of the world’s most durable plastics, and the technology that could be created as a result, is so very important.

The discovery of the waxworm caterpillar’s ability to digest polyethylene marks the beginning of a new era in the fight against plastic. The researchers believe that caterpillars are able to eat and digest polyethylene because beeswax and polyethylene share a similar chemical structure and common chemical bond.  As researchers uncover the precise process that enables the caterpillars to biodegrade the plastic, they move closer to adapting the process into a biotechnical solution for plastic waste. “However,” Dr Bertocchini rightly reminds us, “we should not feel justified to dump polyethylene deliberately in our environment just because we now know how to biodegrade it.”

This story of waxworm caterpillars and a bag riddled with holes might have remained an ordinary story of garden pests and an unusable plastic bag. However, this bee keeper’s mishap in the garden combined with her scientific mind turned an ordinary event into an extraordinary discovery.

Fortunately, we are now closer than ever before to finding a sustainable method to combat plastic waste and it’s all thanks to some very hungry caterpillars.

Find Ebony’s references here, here and here.


Liked this article? Read Sam Jones’ winning entry about imperfect produce.

Heather Catchpole

Author: Heather Catchpole

Heather co-founded Careers with STEM publisher Refraction Media. She loves storytelling, Asian food & dogs and has reported on science stories from live volcanoes and fossil digs

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