It sounds like the stuff of nightmares - spiders the size of a hand which drop from trees on to necks and loose clothing.
And, according to two information boards which have appeared on Mousehold Heath, the East Anglian Drop Spider (Araneaus occumbo) has been introduced into the Norwich woodland.
However, the date that the boards appeared - April Fool's Day - may be a clue that all is not as it seems, despite their professional appearance.
There is no record of such spiders, while the Latin name seems to be a combination of the genus for common orb weaving spiders and the Latin verb to fall.
And the model spiders on trees marked with warning posters fixed to them are further clues pointing to an elaborate ruse.
As is the link people are taken to if they scan the QR code on the fact boards - a GIF of a man trying to catch a massive spider on his ceiling.
The boards, which contain logos of Norfolk County Council, the RSPB, Norfolk Wildlife Trust, Norfolk Nature and the British Arachnological Society, give all sorts of information to make arachnophobes wince.
They state: "Falling quickly from high in the forest canopy, it's easy to see how this fascinating creature got its name.
"Waiting for movement on the ground layer, the drop spider typically looks for gaps or crevices into which it can drop, wiggle and hide away in wait for its prey.
"An open bag, pocket or loose clothing near the nape of the neck can often be mistaken by the drop spider as a safe place to land and has, in the past, been a source of conflict amongst humans and these generally gentle creatures.
"Although their bite can be incredibly painful, they only do so when provoked and there have been no fatal cases in the last 100 years."
The board also features pictures showing people in medieval times fighting off the spiders, as well as photographs claiming to show arachnids sighted in Mousehold Heath and Thetford Forest.
And it states that the last recorded specimen in East Anglia was in a 1646 book by Sir Thomas Browne called Pseudodoxia epidemica.
That book's title translates as 'vulgar errors' and urges people to use reason and science to refute belief in mythical creatures.
The signs have sparked conversations on Reddit and Facebook.
Lisa Bayliss, who posted them in the NR3 Facebook group said: ""The signs look very professional and even now, when I’m sure it’s a prank, a tiny part of me is thinking about a spider dropping on me!"
Were you responsible for the signs or do you know who is? Email dan.grimmer@archant.co.uk
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here