Experts have warned of increased deadly spider activity in Australia after a man was bitten by a funnel web spider that had crawled into his pants.

Speaking from the hospital, tour operator Ross Dixon described how he went to get dressed at his holiday house in Hawks Nest north of Newcastle when he felt a sharp, burning pain in his left thigh.

"I just pulled up my pants when I felt something bite and I realized it was something more than just an ant," he said.

The 58-year-old whipped off his pants, revealing a large black funnel web spider, still alive and crawling through the folds of the trousers.

The quick-thinking Dixon, who has a degree in entomology, captured the spider for further examination and sought first aid at a nearby medical facility.

Paramedics immediately applied a pressure bandage to stop the flow of venom and called in the Hunter Westpac rescue helicopter to airlift him to the Calvary Mater Hospital in Newcastle.

Toxicologists there concluded Dixon luckily only had received a "dry" bite in which a spider does not inject a harmful dose of venom.

Dixon suspected the spider had crawled into his pants as they lay overnight on the floor.

"I had been gardening the afternoon before and I left my clothes on the floor in the bathroom," he said.

"Then I got back into the old gardening clothes this morning and that's when I got bitten."

He did not require antivenom and was released in the early afternoon.

Calvary Mater Hospital clinical toxicologist Geoff Isbister, who took delivery of the offending funnel web in a jar, said males of the species most often bite humans as they wander around looking for a mate.

"You do get people bitten by females but not as often," he said, adding that an average of only one in 10 bites from spiders requires antivenom.

Australian Reptile Park general manager Mary Rayner said funnel webs usually emerge later in the year, from February to May.

"Funnel webs just can't tolerate sunshine and heat — within 10 minutes if you have a funnel web out in the sun you will actually see it shriveling up in front of you," she said.

But recent rain and humidity has brought them into contact with humans earlier than usual.

"This is unseasonal but now that funnel webs are roaming around it is very dangerous for children in the school holidays," Rayner said.

"We need to alert parents to please look out for funnel webs in children's clothing and shoes, especially if they have left them lying outside or on the ground. The same goes for toys and other things like that."

Despite the species' menacing appearance and aggressive nature, Rayner said funnel webs often are misunderstood.

"When they come into contact with a human being they are not biting to kill us, they are biting to defend themselves."