An army of spiders, one as big as a child's hand, have been spotted near some homes in Powys.
Steve Jennings said the spiders were quite aggressive
The mysterious breed, which has a black body with yellow stripes, has set up home outside some flats in Brecon.
Baffled environmental health officers have caught some of the creatures and sent them away to be identified.
It is thought that a large female, who has hatched hundreds of off-spring, could have been an exotic pet that has escaped.
More than 50 webs have been spun in a courtyard near the flats in an area called Friar's Yard.
Resident Steve Jennings managed to photograph the large female spider in a web.
Mr Jennings said: "I came out on the balcony one night and there was this huge spider - it looked like a tarantula. It would not fit into the bottom of a pint glass and is about the size of a child's hand.
"I don't know what they are but they are not the normal type of house spider.
"They are black with yellow stripes on their legs and body, and they are very fast and quite aggressive."
At first, environmental health officers thought the creatures were the tarantula breed, but they do not spin webs.
A Powys Council spokeswoman said: "Following concerns raised by residents, an officer from our environmental health department has visited the site to investigate.
"One of the spiders has been caught and sent away for identification. We are currently waiting for the results."