The spiders have thrown silk snag lines into the air to haul themselves out of the water in Westbury, Tasmania. Credit:Ken Puccetti

"People don't realise how many spiders there are out there until you see events like this," Mr Milledge said, after examining the photographs.

"These mass ballooning events are often associated with particular environmental conditions, for example the flooding that's happening in Tasmania at the moment. I would imagine the spiders are just trying to get away from the water, basically.

"What they do is they climb up to a high vantage point - up to the end of a stalk of grass for example - and then they point their abdomen to the sky and let out a silk thread. The wind captures that and acts like a parachute and carries them off."

A similar event occurred in Goulburn in the Southern Tablelands in May last year, when a resident, Ian Watson, described how his house looked as if it had been "abandoned and taken over" by the spiders.