Female cockroaches can reproduce for years without needing a male, scientists find

Matt Broomfield
Among the world's hardiest animals, roaches can live for weeks without their heads and survive for half an hour under water: Getty/iStockphoto

Common female cockroaches can reproduce for years without needing a mate, producing dozens of generations of all-female descendants, a team of scientists has found.

Parthenogenesis is a form of asexual reproduction, allowing young insects to spawn from unfertilised eggs.

It is the main mode of reproduction for some rarer cockroach species, and also occurs naturally in a range of other invertebrates as well as fish, amphibians, reptiles and even turkeys.

In the case of the American cockroach, the largest roach commonly found across the globe, parthenogenesis was previously thought to be an option of last resort.

But a team of entomologists at Japan’s Hokkaido University has discovered small, all-female colonies of female roaches are able to reproduce many times without needing a man.

“A founder colony of 15 virgin females was sufficient to produce female progeny for a period of more than three years,” the team, headed by Dr Hiroshi Nishino, wrote in their peer-reviewed study.

At one point, there were 1000 descendants of the original batch of roaches thriving in the colony – every single one of them female.

Though that number declined to around 200, the entomologists believe their research goes some way toward explaining how roaches can endure in hostile conditions.

There are 46,000 species of cockroach across the globe, including eight centimetre long specimens found in Australia and even larger varieties in the caves of Central and South America. Some varieties have a 30 centimetre wing-span.

They have been around for 200 million years and have evolved a range of survival mechanisms in that time.

Roaches can live for weeks without their heads, respiring through their bodies, and survive under water for up to half an hour. Some can cover 80 centimetres in a second, equivalent to a human running at 210 miles an hour.

And the latest findings reveal another tool in the roach’s survival arsenal. The scientists stated: “in the short term, especially in the presence of abundant resources, parthenogenesis can be a useful strategy for rapidly generating large numbers of female progeny and colonis[ing] new habitats.”