A Dunedin man was recently bitten by a spider and required medical treatment.
Pest exterminators were then asked to remove what another person termed a "plague" of spiders at the family house.
Another man, who lives near St Bathans, was also recently bitten by a spider, became "very sick" and required hospital treatment, with antibiotics.
Pest-Gone Services owner Ben Powell said he dealt with one or two cases of white-tailed spiders in Dunedin houses each week.
While-tails are slim grey spiders with a distinctive white-tipped tail.
They also have a painful bite which can lead to infections.
Warmer weather and growing community awareness of the poisonous exotic spiders could have led to more people noticing white-tails in the South this year, Mr Powell said.
During the past 10 years, callouts to deal with these spiders had greatly increased, MrPowell added.
A trend towards increased installation of heat pumps and home insulation also meant many houses had become more welcoming for other spiders and insects.
White-tailed spiders were solitary hunters. Instead of using a web, they ran to catch other spiders or insects, often in the evening.
Warm weather in Dunedin now more often continued into winter, and encounters between people and white-tailed spiders could increase in future.
Mr Powell had encountered some exotic redback spiders in the city, but they preferred dark areas, and to build their webs under the house, resulting in less contact with people.
In earlier comment, Adrian Adamson, of Summit Pest Management, said the firm had received "more callouts than normal" about white-tails during summer.
White-tails were most commonly found on the Taieri because temperatures there were warmer than in other Dunedin suburbs, and the firm received more callouts about them in Mosgiel than Dunedin, Mr Adamson said.
