A Mardi Gras cockroach. Image Credit: Su RamMohan

Our native cockroaches aren’t as gross as you think

  • BY Angela Heathcote |
  • April 11, 2018

Don’t let the cockroach that feeds on your forgotten leftovers stop you from appreciating these native beauties.

AUSTRALIA IS HOME to more than 550 cockroach species, and that’s just the ones science has so far described.  But before you recoil in disgust and begin dry-retching, hear us out. 

Of these 550 described species, only six are considered pests, and of those only two are native. The other four have been introduced and are certainly not lovable.

You’re likely to see either the German or American cockroaches in your unwashed breakfast bowls late at night, not our colourful, charismatic natives.

Rather, these natives prefer deep and intricate burrows that they dig in the country’s semi-arid region or cushy leaf litter on the ground below our eucalypt and acacia trees.  The well-recognised bush cockroach, which sometimes goes by the alternate name of the Mardi Gras cockroach (Polyzosteria mitchelli) because of its bright colours, is so beautiful that some people mistake it for a beetle.

See more: Jewel beetles: Australia's flying gems

Australia’s cockroach man

David Rentz, author of the Guide to Australian Cockroaches and former director for 25 years of the National Insect Collection at CSIRO, sees beauty in most, if not all, of our native cockroaches.

But they aren’t his first love. David has been obsessed since he was six-years-old withspecies of Orthoptera— the animal order that includes cockroaches, katydids, crickets and grasshoppers.

He’s already produced a guide to our native katydids, just completed his guide on cockroaches and is currently working on a guide to our native crickets.

See more: These shocking katydids are one of Australia’s weirdest insects

Having moved to Kuranda in tropical North Queensland, which David notes is home to more than 93 species of cockroach, he became more familiar with their ecological importance.

“You could pick up just a handful of leaf litter and you’d find many small, native cockroaches crawling around it; easy food for lizards and birds,” he tells Australian Geographic.

“They’re also the world’s best recyclers as they’re heavily involved in the breakdown of leaves into the soil.

“Then there are those brightly coloured ones that are actually diurnal and you see them lounging on flowers and with pollen tangled in their hairs, which makes me wonder whether they’re pollinators.”

His favourite, the giant burrowing cockroach (Macropanesthia rhinoceros) is roughly the size of the palm of your hand, can live for up to six years and it hisses. Yes, you heard correctly.

“Some cockroaches hiss and others make a peculiar buzzing sound,” David explains.

“The hissing might be a way to encourage a predator to drop them, a sexual attractant or perhaps it’s just a sound they make when they’re feeling threatened.”

giant burrowing cockroach

(Image Credit: Matthew McLean/Bush Heritage)

A bad reputation

Despite their unique appearance and characteristics, and the way they’ve managed to adapt to some of Australia’s harsh environments, our native cockroaches still get a bad rap.

“In Australia there are fewer than six species that give the whole group a bad name,” David reiterates.

“A lot of Australians live in cities and the cockroaches you see in restaurants and homes are awful and should be controlled because they can transmit disease.

“Most, if not all of these invasive species cannot live away from these domestic situations. Out in nature they die. So you rarely see an introduced cockroach in the wild.”

Not all Australians, however, lack a reverence for these insects.

David says that some of the patterns seen in Aboriginal art look quite similar to those that decorate the backs of our native cockroaches and grasshoppers.

“Images of these insects have been shown to various Aboriginal people and they’ve been astounded by the similarity between the colours and patterns of these cockroaches to some of the facial patterns they wear during their ceremonial dances,” David says.

“I always wonder whether their closeness to nature has influenced their artistic output and they’ve replicated these gorgeous patterns.”

Where are all the entomologists?

David started at the CSIRO back in the 1970s as the director of the National Insect Collection, which according to the CSIRO grows by more than 100,000 specimens each year.

One of David’s biggest concerns is the dwindling number of entomologists equipped to study all that resides in the collection.

“We’re becoming a smaller and smaller group because there are very few jobs in entomology.

“The universities have decreased the amount of courses they teach. Some have maybe one or two units but there used to be entire buildings dedicated to entomology.

“There is definitely an interest in insects but because of the job situation, not many people want to get higher degrees in entomology.”

Despite being in retirement, David continues to add his discoveries to the CSIRO's collection and regularly contributes his vast knowledge of Orthoptera to the entomological field.

“There are so many undescribed things to deal with and the ones I collect are sent straight to the insect collection and they sit there like books in a library waiting for someone to come along and study them.”

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