Mid Canterbury residents are getting buzzed off by a plague of cluster flies terrorising houses.
The flies congregate in groups the size of tennis balls or even bigger, in the warmer parts of houses.
Alan Kerr, of Ashburton Pest Control, said he had only dealt with three cases of a cluster flyinvasion in Ashburton so far, but "I'm sure there is more out there".
"They are becoming quite a big issue. We aren't talking about five flies hanging around a light, we're talking about thousands. They're filling up people's homes."
Mr Kerr struck his first case two weeks ago, followed up by a nasty one recently, where he was surrounded by thousands and thousands of flies in a client's ceiling.
He said cluster flies hibernate over winter in ceilings and high parts of people's houses, once it's spring they make their move.
"Problem is, that if you shine a light on them they think it's spring, and they just go nuts.
"They get into people's houses and go everywhere. In most cases people don't even realise they're there."
The problem seemed to be worse in rural areas where there was less concrete and more pasture, Mr Kerr said.
Larger than the common house fly and smaller than the average blow fly, the cluster fly is dark grey with a green or blue tip.
As a maggot, the cluster fly feeds on worms, and has developed a particular liking for New Zealand's native earthworm, hence the attraction to rural areas.
But fortunately they're easy to deal with. Because they're so "dopey" and slow moving, the best way to get rid of them was simply to vacuum them up.
