The ‘cannibal’ spider is said to have a ‘bite like a deep injection’ - and their natural habitat are houses.
It is one of the Segestria Florentina species. Some common names include tube web spider or cellar spider, although neither are exclusive to this species.
And experts say they are becoming a more common sight across southern England.
Matthew Sutherland found the creature outside a chcolate shop in Folkestone, Kent, on Tuesday.
The 34-year-old said: “I wouldn’t want any contact with it - but I have never seen such an interesting looking spider.
“It looked amazing, we were advised that it is a harmless spider as long as it isn’t threatened or provoked.”
Theresa O’Connor, 40, took some photos of the menacing-looking spider before it crawled into a hole in a wall.
She said: “I approached him and he didn’t move, so I started taking photos - it didn’t bother me, I love spiders.”
According to nature expert, Owen Leyshon, the spiders thrive off living inside brick work.
He said: “These spiders are dotted around the county and with hotter summers and warmer winters, there may be more.
“I can see these potentially increasing in range - they have amazing green fangs on them, which make it a distinctive spider.”
Owen, who works for the Romney Marsh Countryside Partnership, added: “The spiders live in gaps of very old and dry traditional brick walls.
“They do have a bite but only when they feel threatened - certain people will react differently to pain so it depends on the person.”