If the house spider originally came from outside the UK, it might have first arrived in castles and stately homes inside packing crates.
So, are the spiders in castles and stately homes the direct descendants of spiders that arrived in those buildings a few hundred years earlier?
If they did DNA tests on house spiders in different castles would they find that they were genetically diverse because of being in those castles for centuries? By which I mean, do spiders in Balmoral have DNA that’s different to the DNA of spiders in Windsor castle?