Some people are worried that the spiders that start appearing in autumn are banded together into small gangs hell bent on mischief. That couldn’t be further from the truth, and the reason the numbers get smaller is largely due to the effects of these big spiders on each other. They are often extremely territorial, and in the photo below you can see a female being driven from her web in an old shed by another female of roughly the same size.
The spider left her home and fled while the newcomer decided to set up camp, and made the fatal error of straying to close to a neighbouring False Widow (Steatoda nobilis) which made short work of her. Almost all spider species will prey on each other, and sometimes members of the same species (cannibalism) but it is important to realise that the difference between one spider species and another can be as vast as that between a human being and a cow or any other mammal, and maybe even more so.
Despite the massive appearance of large Tegenaria duellica House Spiders (the legs would easily span the palm of my hand) the bodies are never quite so large as they appear to be. The largest House Spider I ever saw appeared to have an abdomen of three centimetres in length (an inch) but when I measured it accurately with a scientific ruler I was very surprised to discover its body measured exactly 23 centimetres. And, of course none of these species are the largest in Ireland. That honour falls to a much more impressive creature, the Raft Spider, Dolomedes, which lives in swamps and bogs and hunts frogs and small fish among many other things. When I get a good photo ( I have a bad one) I’ll post something about that very handsome monster.