Tag Archives: Tegenaria

A Video Identity Guide to Autumn Irish Spiders

This is a little rough and ready video programme I recorded and which my brother Owen edited together to help people identify spiders they find around their houses in Autumn. There’s a little more to come but this should explain a lot, if you can put up with my voice for 18 mins:

The Last of the Big Spiders this year

I think many of you will be delighted to know that big spider season is ending soon. These big spiders which come into houses in autumn, are looking for mates. These unseen females are much stockier than their suitors, and generally stay in their webs, often hidden from pulic view. In order to let their boyfriends find them they release pheromones onto the air, and the males come running.

The biggest spider I have seen so far this season, a male Tegenaria duellica (sometimes called t. gigantea) House Spider. Just like all creatures confronted by an immense human monster, it fled and tried to climb the side of this old bath, in which I have grown potatoes.
The biggest spider I have seen so far this season, a male Tegenaria duellica (sometimes called T. gigantea) House Spider. Just like all creatures confronted by an immense human monster, it fled and tried to climb the side of this old bath, in which I have grown potatoes.

The males then live for a number of weeks or months in the webs with the females and leave before the young are born, or are killed and eaten for overstaying their welcomes. As a result, sensible males who leave early can grow to immense size and apparently live quite a few years. But by now most of the females have mats and will stop releasing pheromones and the males will go back to their regular lives, if they avoid the various predators that delight in eating them, especially Robins and Blackbirds, but Wrens too.

A few more notes on Autumn Spiders

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 Tegenaria on the left is still sitting in the extremities of her web, but the intruding spider on the right is much closer to the entrance, preventing her from returning.

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.

A large and dark female False Widow, Steatoda nobilis, with a large House Spider as prey. Spiders are an important part of many spiders prey.

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.