Scientists at the Yorkshire Museum set and monitor traps to capture invertebrates living in the Museum Gardens.
On March 8, staff checked the devices and found a male 'Dicranopalpuls larvatus' - a species of spider-like arachnid better known as a harvestman.
This species was only recorded in the UK for the first time in 2020, and though it has been spreading through the country, the York find is the furthest north it has been discovered so far. The next nearest recording was in Norfolk.
The harvestman is known for its 'Mask of Zorro' colouration across the eyes and extremely long legs - their bodies are only 2mm in length but each of their eight legs can measure up to 20mm.
It is not the first time a rare species has been discoverd in the Museum Gardens - in 2018 a type of leaf-mining fly was found on a sage bush, the first time it had been seen in the UK.
A statement from York Museums Trust read: "This harvestman was first recorded in the UK in 2020 and is now popping up all over the place. It might not be to everyone’s liking but this discovery highlights that there is a whole fascinating, hidden, world of insects and invertebrates going on all around us. Only by looking closely can we see some of these amazing lives in detail.
"It is only by looking that we can find these creatures and there are always new discoveries to be made."