Dead in the act: moth mating aftermath stuns

A group of dead moths at Momona last week after what is believed to be an early mating season....
A group of dead moths at Momona last week after what is believed to be an early mating season. Photo: Anne-Francis Barkman
Ending a comfortable life as a caterpillar by taking to the sky for an orgy that will result in hundreds of deaths.

Welcome to the existence of a summer porina moth, the kind that have been showing up dead across Momona.

The reports first showed up early last week, when social media users congregated online to try to figure out what was going on.

People had found them laying dead near their homes and huddled around cars near Dunedin Airport.

Photos were posted accompanied by a feeling of distress.

"What the actual f... is happening?" one woman asked.

Weed spraying, climate change and chemtrails were all proposed as potential causes.

Some celebrated the mass deaths, citing their hatred of the furry insects.

"Best thing that could happen ... I am terrified of moths," one said.

"Good riddance," another wrote.

It may seem apocalyptic, but in reality the moths were simply engaging in a vital part of their breeding cycle, University of Otago botany Associate Prof Janice Lord said.

The moths had distinctive white marks on their wings, which suggested they were summer porina, scientifically known as Wiseana copularis.

After spending most of their life as a "happy, fat" caterpillar, they would undergo metamorphosis and emerge as a moth — but without a mouth.

With no means to feed, the summer porina was born with a set amount of time before they ran out of energy and died, she said.

Mating was the ultimate goal, resulting in "massive frenzies".

The event typically happened later in the year, around March. However, a combination of warm weather and rain made for ideal breeding conditions.

Finding a mass of dead insects might seem like walking in on a disaster site, but it was actually a sign of a good breeding season.

It may sound like the moths end their lives by going out in a blaze of glory, but not all of them are so lucky.

Light pollution was an issue, as the nocturnal insects were drawn to anything bright.

Some lights, such as blue LED streetlights, were so powerful that the moths were so enthralled they ran out of time before being able to mate.

The porina moths are considered a pest by some, as they are damaging to introduced pasture grasses, such as ryegrass.