Tag Archives: False Widows

False Widow Spiders

Unfortunately this week I have been a bit slow on the draw when it comes to posting, but here at last are photos of False Widows to help you identify them. It seems they have been in the south of the country in small numbers for over a century, but with the mild winters of the 1990s and 2000s they spread about the island of Ireland rapidly, aided greatly by the sheer amount of activity of  the Celtic Tiger.

A classic example of a female Steatoda nobilis, the larger of the two common False Widows found in the British Isles. She is very similar to the female Missing-sector Orb-weaver spider, but much larger.
A classic example of a female Steatoda nobilis, the larger of the two common False Widows found in the British Isles. She is very similar to the female Missing-sector Orb-weaver spider, but much larger.

Anyhow, the first thing you need to know is that they get their name because of their resemblance to the true widow spiders, the Lactrodectids, They are identical in size and shape and sometimes in colour, depending on the species.  And, most importantly, they are also venomous to humans, but much less so than the true widow spiders. However, if you have an allergy to their bite then it might as well be a true widow spider, and you immediately need medical help. How do you know if you are allergic? Simple, you will also be allergic to bee stings. The acid in bee stings is almost identical to the acid in the venom of these spiders, and to the acid in nettle stings. Crushed leaves of the Dock plant are very effective at treating all three stings if you are not allergic, as is a little baking soda dissolved in water, as these things are alkalis. If you are allergic or get any sort of large swelling after a bite, whatever the biter was, always seek medical help immediately. Don’t try to tough it out.

A dark female specimen of Steatoda nobilis.
A dark female specimen of Steatoda nobilis.

The female Steatoda nobilis can be very dark, as in the photo above,  but the slightly smaller Steatoda grossa can be as shiny and black as a black currant, and is much more easily confused with the infamous Black Widow. The usual patterns that distinguish the species can often only be seen under a strong light, such as from a flash bulb. False Widows spend almost their entire lives hanging upside down and are very slow-moving. If they are attacked they normally pull their legs in tight to their bodies like a tortoise and drop to the ground to wait until the danger has passed. They mostly get onto humans (a rare enough event) when they are accidentally carried away in items from sheds.

A male Steatoda nobilis trying to convince a female to mate having blocked her retreat into the hollow rung of an upturned ladder. He has very red legs and is as large as she is although his abdomen is much smaller. Pregnant females will have swollen and shiny abdomens about the size of a black currant or a little larger.
A male Steatoda nobilis trying to convince a female to mate having blocked her retreat into the hollow rung of an upturned ladder. He has very red legs and is as large as she is although his abdomen is much smaller. Pregnant females will have swollen and shiny abdomens about the size of a black currant or a little larger.

Unlike true widow spiders, the males of False Widows can be almost as big as the females, and well capable of bullying a female into mating. The true widows don’t stand for that behaviour, which is why they become widows so soon. But their males are much smaller than them. Right now, in Autumn the male Steatoda nobilis spiders are roving around still looking for females. They climb walls outside houses where the females usually wait quietly under the eaves. Some males do get eaten, but this year every male I’ve seen successfully mated and escaped to mate again. That’s probably why they grow as large as their females.

A magnificent example of a male Steatoda grossa False Widow, seen not now but in the spring, their time to wander round. they don't get very big though, but big enough if you don't like spiders.
A magnificent example of a male Steatoda grossa False Widow, seen not now but in the spring, their time to wander round. They don’t get very big though, but big enough if you don’t like spiders.

Although the female Steatoda grossa is very similar in habits to the larger S. nobilis, they much more readily enter houses, particularly sheds and quiet and cool attics. They arrive as tiny spiders and stay put only if they are not disturbed. The male S. grossa is completely different to the female. He seeks her out not in autumn, but in the springtime. Larger ones can resemble the long-legged running House Spiders that terrify people every autumn but they are not nearly so big and can be very brightly coloured. Above is a classic example of a male Steatoda grossa, which prefers running along the ground to climbing around upside down, until he finds a mate. He is clearly built for running.

Now, that mostly takes care of False Widows but I will be uploading a video soon which some people will probably find more useful as the behaviour of various spiders is more obvious.

A few words on spiders…

A lot of people have been contacting me lately regarding spiders, mostly to do with identifications. Many have said they cannot find suitable guides for Ireland, so I draw your attention to my own little publication, Irish Spiders, which is available from Amazon on the Kindle at:

http://www.amazon.com/Irish-Spiders-ebook/dp/B00ALJ8JTE/ref=sr_1_1?ie=UTF8&qid=1367679075&sr=8-1&keywords=Irish+Spiders

If you download Amazon’s free Kindle Reader onto your phone, laptop, tablet or PC, then you can get this guide and always have it handy but some of you have been deeply concerned about the False Widows.

My photographic guide to spiders, available at: http://www.amazon.com/Irish-Spiders-ebook/dp/B00ALJ8JTE/ref=sr_1_1?ie=UTF8&qid=1367679075&sr=8-1&keywords=Irish+Spiders
My photographic guide to spiders, available at: http://www.amazon.com/Irish-Spiders-ebook/dp/B00ALJ8JTE/ref=sr_1_1?ie=UTF8&qid=1367679075&sr=8-1&keywords=Irish+Spiders

At this time of the year False Widows are on the move and, of course, we humans too are on the move, outdoors into our gardens to sow and plant, sit in deckchairs and have barbecues, so there are far more spider encounters than usual. But don’t worry, False Widows do not set out to bite people, most people feel little or no ill-affects when they do bite, and they are not particularly venomous, even when the venom does have an acute affect. Very handsome specimens of the smaller one, Steatoda grossa, have begun turning up quite a lot lately, such as the one pictured below.

A female of the smaller False Widow species found in Ireland, Steatoda grossa. these spiders are often shiny black, but this dark purple with cream marbled patterns are classic markings. Unlike Steatoda nobilis, S. grossa has arrowhead markings running up through the middle of its abdomen, as you can see in this photo.
A female of the smaller False Widow species found in Ireland, Steatoda grossa. these spiders are often shiny black, but this dark purple with cream marbled patterns are classic markings. Unlike Steatoda nobilis, S. grossa has arrowhead markings running up through the middle of its abdomen, as you can see in this photo.

For those who want to actively discourage these spiders, then your best friend is another spider, the Long-bodied Cellar Spider (Pholcus phalangioides), which is especially common on the east coast of Ireland. This long-legged spindly spider is a dedicated hunter of other spiders, no matter how large or toxic they are. I have seen them kill the very largest House Spiders, and False Widows, and only yesterday got a nice shot of one with a much larger Windowsill Spider (Amaurobius species) in its jaws.

A Long-bodied Cellar Spider feeding on another species. They also actively hunt, kill and eat False Widows.
A Long-bodied Cellar Spider feeding on another spider species. They also actively hunt, kill and eat False Widows.

 

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.