or a spider?
The False Widow, a purple and black creature with a body the size of a 1p piece, is said to carry enough venom to kill a human.
Since arriving in Devon from the Canary Islands, the spider has established colonies in Devon, Dorset and Cornwall.
The spiders do not usually survive in colder parts of the UK, but a series of mild winters have led them to migrate to other areas.
Spider recorder David Haigh, of Cheltenham, has reported sightings of the species in Gloucestershire and Wiltshire.
One was in a shed in Tewkesbury and the other was spotted in Longney, he said.
The False Widow is one of 12 arachnid species known to bite humans in the UK.