Weather radar catches massive bug swarm over New Zealand's North Island

A vast swarm of bugs that covered much of the northern half of the North Island of New Zealand on Thursday night and Friday morning has been caught on the Metservice weather radar. MetService do not know what it was and entomologists are puzzled.
One was convinced it was the Tasmanian grass grub and another suspected huge swarm of aphids. Metservice's Peter Kreft said the unknown insects began swarming over the Waikato region at around 9pm on Thursday. "They were pushed by the south easterly wind north toward Auckland," he said.

By around 7am on Friday the massive swarm was out over the Tasman Sea, west of Auckland. Kreft said the weather service was not sure what it was.  "We strongly suspect the echo is swarms of insects," Metservice says.

"To show up in radar imagery like this, they must be about as large as, and as numerous as, precipitation particles.... We see this from time to time, but this one is a very good example of it." Entomologist Stephen Pawson of Scion, a Crown research institute said at a guess the timings favored Tasmanian grass grub (aphodius tasmaniae), an introduced agricultural pest.

There's an animated gif showing the movement of the swarm here.