Scientists discover why the world will never be rid of cockroaches – and it’s really bizarre

COCKROACHES have been around for almost 300 million years - surviving the dinosaurs and barely changing shape.

The smelly critters have been known to infect our food and are considered a pest - but are very tricky to get rid of.

And now scientists have discovered why the pesky critters are able to multiply so quickly - and warned that they are a "threat to public health".

The American Cockroach (or Periplaneta americana) are able to give birth without ever having sex thanks to a phenomenon called parthenogenesis.

Parthenogenesis produces all female litters - who in turn produce their own set of daughters.

A team at Japan’s Hokkaido University began monitoring the species to work out why they are so resilient.

And during their observations, they discovered that just 14 virgin cockroaches could sustain FOUR generations.

Over three years the colony grew exponentially - and at one point had around 1,000 all-female roaches clambering over each other.

The female American roach is typically larger than the male - and more likely to survive harsh environments.

And this in-breeding is more likely to spread nasty infections to humans.

In their research, which was published in Zoological Letters, lead authors Ko Katoh and Hiroshi Nishino wrote: "Maintaining certain populations of Periplaneta [American cockroach] for more than four generations over a period of three years only by parthenogenesis is a threat to public health because of their potential roles as vectors for pathogens and allergens indoors."

Their main fear is that infestations can survive without males, making it tricky to curb the cockroach population.

A popular infestation treatment relies on luring males with fake female hormones to exterminate them - but this research suggests the method is defunct, Nishino claimed.

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