Cockroaches can breed for generations without males, study finds.

Female cockroaches can reproduce healthily for years without ever meeting a member of the opposite sex, a Japanese study has found.

Researchers from Hokkaido University isolated 15 virgin female cockroaches in 2013. Within three years, the female-only colony had bred five generations and only showed small signs of slowing down.

While this phenomenon is not unheard of in the insect world, etymology expert David Merritt from the University of Queensland’s Faculty of Science said the fact the cockroaches could breed for so long was unusual.

“Many insects can reproduce parthenogenetically, meaning females don’t need to mate to produce offspring, but usually they go extinct,” Dr Merritt told the ABC.

“But [this study] kept the cockroaches for many generations.

“So not only are they reproducing parthenogenetically, but they seem to be quite fit. They’re not as sickened as colonies seem to have been shown in the past to be.”

The study, published in journal Zoological Letters, only covered the American cockroach species, but don’t let its name fool you: it is one of the most common cockroaches found in Australia.

They tend to hang out around sewers, and can spread disease-causing bacteria onto food.

“The fact that isolated populations can be maintained just by females reproducing asexually is a bit of a concern because it means that you’ve got to kill the whole population to kill them all,” Dr Merritt said.

Parthenogenetic reproduction — that is, reproducing asexually — tends to occur as a last resort when there are no males present.

In this study, the grouped females picked up a signal from each other that started the male-free breeding process.

“They recognise the fact that there’s a whole bunch of females around, there’s no males around, so they’ll go into this different reproductive pathway where they produce young without being mated,” Dr Merritt said.

“It’s like a sisterhood.”

The Hokkaido University study said the sisterhood-like behaviour could also indicate an early stage of “social cooperation” among the cockroaches, usually found in more advanced insects like termites.

This post originally appeared on ABC News.