A gangly insect spotted on a car door in a British seaside town has turned out to be one of the strangest discoveries ever to hit New Zealand ecology.

After amateur wildlife photographer David Fenwick snapped the insect outside his home in the Cornwall town of Penzance, the creature was identified by a pair of entomologists.

The fact it was a native New Zealand stick insect was nothing extraordinary - the species are famed for globe-trotting and a population has existed in the UK for a century, having likely hitched a ride in the soil of imported plants.

What was remarkable, however, was the fact this bug was a bloke.

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Previously, all collected specimens of the endemic Acanthoxyla genus have been female, and understood to only use parthenogenesis - a natural form of asexual reproduction.

Massey University evolutionary biologist Professor Mary Morgan-Richards was awed at the find.

The simple answer: the male was a mutant.

"Females usually only produce sons if there is a father - but as these New Zealand stick insects are always female, they produce all genetically identical daughters," Morgan-Richards explained.

"We call them obligate parathenoegnetic because there are no males they can not use sexual reproduction."

However, she added, males still might be produced if a chromosome was lost during egg production.

Females possessed two X-chromosomes, but males were produced if there was just one X-chromosome, along with the other normal chromosomes.

"Stick insects don't have Y-chromosomes. A mistake at cell division could result in an egg missing an X-chromosome - and thus a mutant male is hatched."

What made this male even more special was the fact most Acanthoxyla were triploid - meaning each cell has three of each chromosome - and theoretically couldn't make a male with just one simple mistake.

Previously, all collected specimens of the endemic Acanthoxyla genus have been female, and understood to only use parthenogenesis - a natural form of asexual reproduction. Photo / File
Previously, all collected specimens of the endemic Acanthoxyla genus have been female, and understood to only use parthenogenesis - a natural form of asexual reproduction. Photo / File

"So I thought we would never see a male acanthoxyla in New Zealand - and certainly not in UK."

Morgan-Richards said there were so many people in the UK that unusual bugs tended to be spotted more easily, and records showed more than 2600 stick insects had been sighted in the wild there.

Of those, a little more than 1000 had been documented with a photograph - suggesting a rarity for the male of around one in 1000.

She described the weird discovery as "record-breaking and exciting", and something that offered credibility to the possibility of past and future gene flow between New Zealand stick insect lineages.

"Fortunately, we are not very worried that these stick insects could go extinct. They are widespread and fairly common and can eat anything green.

"But being parthenogenetic might make them more vulnerable to large-scale changes."

However, as their habitats and the climate changed, it was likely their selection for new abilities would grow stronger, she said.