Mystery surrounds hundreds of black beetles: Te Atatu South.

Caryn Wilkinson Reporter from Community News

Mystery surrounds the gathering of hundreds of South African black beetles outside Countdown Te Atatu South on Tuesday night.

Concerned shoppers posted on a Facebook community page that they had seen a swarm of the critters on the footpath, spreading to the carpark.

A resident reported a security guard was trying to sweep them from the door outside the supermarket.

Beetle scientist Rich Leschen from Manaaki Whenua Landcare Research said the South African black beetles were nocturnal creatures.

"They're active at night, flying around looking for mates."

Leschen said the huge number of beetles may have been attracted to the bright artificial lights outside the west Auckland supermarket.

"They're really gathered there by the light, not there to get toilet paper," he said.

"One thing is they will probably be more active with the warmer nights which is normal for a lot of insects in general.

"They might be more active because of the rain."

Leschen said the adults were harmless but large numbers of larvae could remove the leaves of some trees, according to literature.

"I haven't seen them defoliate leaves here," he said.

"In my opinion, I think they're probably more critical as turf and pasture pests.

"Everyone probably has them in their garden. The blackbirds are able to find the larvae when they're close to the surface and they dig 'em out from the tufts in the grass."

Leschen said there were thousands and thousands of species of beetles in New Zealand with many more yet to be discovered.

He decided to study natural history when he was a young biology student, "so I just gravitated to beetles, maybe because there's so damn many of them."

Leschen said his affinity for the insects evolved over time and was unrelated to a traumatic childhood encounter.

"I think I was three years old and I stuck my finger in its mandibles and this is quite a large beetle in the United States," he said.

"It bit me and I hated it. I was screaming and crying and I killed it.

"It didn't really influence me at all to work with beetles."