Clean living and sophisticated - the true-blue roach

23 May 2003

Professor Haley Rose with native Australian cockroach
Professor Haley Rose with native Australian cockroach

By Alison Handmer

A species of a wood-feeding cockroach, at risk of extinction on Lord Howe Island, has found a champion in Associate Professor Harley Rose.

More highly evolved than the introduced common kitchen cupboard varieties, the native Australian cockroaches are environmentally friendly and wouldn't be seen dead in a house, according to Professor Rose, acting Pro Dean of the Faculty of Agriculture, Food and Natural Resources.

Some live in burrows in the soil, venturing out after dark and early in the morning to retrieve dead leaves which they turn back into soil nutrients. Others live in decaying wood, where they assist with the process of decomposition.

"They are incredibly clean," said Professor Rose, who first began working with the insects in 1977, intending to breed them as "laboratory rats" for research which might shed light on how insects in general become immune to pesticides so quickly.

Native cockroaches are much bigger than introduced species. In northern Queensland, one species can weigh as much as 30g, and measure up to 80mm in length.

"I became fascinated by the burrowing cockroaches and found that there was very little known about them," Professor Rose said. He started to look for species along the east coast of Australia, keeping them in honey pots in the faculty's laboratories and becoming engrossed by their life cycles and habits. In the early 1990s he even sold them as pets to acquire funds to support his research.

"I have never used one for insect toxicology, mainly because they are difficult to rear in the laboratory and have a long life cycle which is not conducive to large numbers," he said. "I concentrate now on their biology and their taxonomy.

"Ten species had been identified when I started, and now I have collected another 15 new species, some of which I am still describing."

The cockroaches mature in three years, digging burrows about a metre underground. Females give birth to live young, a sign of sophistication in the insect world, and raise up to 30 young at a time in individual burrows. They live for about seven years.

"The male will go down a burrow and find a female that is just about ready to become an adult. They will mate and after the first rain, he will leave and either make another burrow or find another female." The females, who reproduce once a year, store the male's sperm throughout most of their life.

Native cockroaches are wingless, and members of each particular species tend to live in relative isolation, making them ideal for population and evolution studies. On islands off the east coast of Australia they have been isolated from the mainland for up to 20,000 years.

Professor Rose has studied a small colony of wood-feeding cockroaches living on Blackburn, an island in the Lord Howe Island lagoon, and has recommended to the National Parks and Wildlife Service that they should be added to the threatened species list.

He believes the main Lord Howe Island population was wiped out by the same rats that exterminated the unique Lord Howe Island stick insect population on the main island after a shipwreck in 1918. "The big ticket item would be to get rid of the rats on the island and then re-introduce the cockroaches," he said.

Some soil burrowing species continue to eat leaf litter and breed in the honey pots in Professor Rose's laboratories, obligingly crawling up his fingers to be photographed. One was born in captivity in 1997 from a female captured in 1993. "They make great pets but are fairly sensitive to their living conditions. There is still much to be learned about these fascinating creatures," he said.

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