“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 Professor 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.
