Save the Lord Howe Island wood-feeding cockroach!

Save the cockroach

My “next big thing” is a field trip to Lord Howe Island to do some work on a cockroach. It was wiped out on the main island by rats, but there’s a big push to reintroduce the unique arthropods that survived there now that the rats have been exterminated.

The rats got on to the island about 100 years ago, and they’ve been devastating for several bird and plant species plus a number of other creatures. Getting rid of them has been a major success story. Most people know about the stick insect that the rats wiped out – it was a kind of very large tree lobster, thought to be extinct until an expedition in 2001 found a small population surviving on Ball’s Pyramid, an uninhabited island about 23km away. There have since been some successful breeding programs to bring them back, and there are plans to reintroduce them onto the main island.

A lord howe island stick insect, large black insect covering most of someone's palm
The Lord Howe Island stick insect. Credit: By Granitethighs – Own work, CC BY-SA 3.0,

This unique Lord Howe Island wood-feeding cockroach was also wiped out following the rat invasion. Searches over the last few decades have revealed that there’s some still remaining on a couple of tiny little islands within a few hundred metres of the main island. We’re going to do some DNA studies of the ones on those little islands, then compare them with some museum samples that were taken before their eradication by the rats. If we can show that the living cockroaches on these little islands are quite similar to the ones on the main island, that gives us a reason to reintroduce them to the main island.

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Anything to do with cockroaches can be a pretty hard sell. But these are quite cute little things, and very benign.

Termites have kind of cornered the market, as there aren’t a lot of other organisms that are able to eat cellulose.

My interest in arthropods happened by chance. I actually started out on a medical science degree, but by the end of the third year I was thinking it wasn’t for me. Someone pointed me in the direction of an academic named Michael Slater who was working on termite biochemistry, studying the enzymes that termites used in their guts to break down wood. I haven’t looked back.

During my PhD, my Japanese collaborators and I found the genes that encoded those enzymes, which were the first of their kind in animals. I was wondering where these genes came from, and from there I really got fascinated in evolutionary biology. Once I started comparing termite DNA to cockroach DNA, it became very clear that termites were a kind of cockroach. That was one of the main discoveries during my PhD.

Photo of round black cockroach on rock: the lord howe island wood-feeding cockroach
Panesthia lata, the Lord Howe Island wood-feeding cockroach. Credit: Mike Letnic

Termites are so important to our ecology. They have astoundingly high biomass; if you look around the tropics, in terms of kilograms of biomass, termites outweigh most other organisms. Ants are up there as well, but termites basically feed on wood and other organic matter – they’ve kind of cornered the market, as there aren’t a lot of other organisms that are able to eat cellulose. That’s because they have these symbiotic microorganisms that live in their guts that help them to break down the cellulose. And for that reason, they’ve become very dominant.

In the top end of Australia, termites are keystone species. They’re recycling all of the plant material and enhancing the quality of the soil. Air is about 80% nitrogen, and they’re able to convert that nitrogen into protein with the help of their symbionts, and that improves the fertility of the soil. Their mounds are impressive sinks of nutrients, and provide a year-round food source for a lot of different kinds of invertebrates and vertebrates. Our cathedral mound termites build the tallest termite mounds in the world.

Most cockroaches are out there just working for free making our ecosystems beautiful.

The fact is only a very small percentage of termites cause problems for humans. There’s probably around 4,500 species of termites, and 98% of them are just doing good work, recycling and keeping the ecosystem functioning by turning over all that carbon. And you can say the same with cockroaches: there are about 3,000 species of cockroaches and only a very few of them ever come into contact with humans. Most of them are out there just working for free making our ecosystems beautiful by being a food source or, again, recycling.

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It would be good for people to realise that these organisms are actually useful. If people appreciate nature and like to go bushwalking or camping, part of the reason these places are beautiful is because all these insects and other invertebrates are working behind the scenes to keep things going. Maybe then people would think twice before spraying insecticide willy-nilly around their homes. Some people spray their whole gardens just to get rid of something that’ll come back next week.

Some people spray their whole gardens just to get rid of something that’ll come back next week.

A bigger problem is agriculture. Any outdoor use of insecticides is likely to result in them getting into our waterways, and they’re often very nasty to aquatic life. I’ve just begun collaborating with some biochemists to design novel insecticides that are very specific. These insecticides would target a small group of organisms so that if you do have to spray it widely, at least you’re not killing everything off.

We’re using quite sophisticated methods that are often used for discovering medicines and drugs against cancer. It’s still very early stages, but it’s looking promising and could be the next big thing. At the moment there’s a risk of extinction of a lot of insects – our insects are in trouble due to the massive application of insecticides in certain areas. It would certainly be a big thing to minimise that impact.

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