Tag Archives: venom

Spiders and Cases of Mistaken Identity

The Missing-sector Orb-weaver, Zygiella x-notata, above, can sometimes be mistaken for the False Widow Steatoda nobilis, but is usually much brighter in colour, smaller in size and makes a completely different web.

Many spiders are very similar, and there is a lot of worry of some of them due to the colonisation of Ireland by False Widows in such numbers these days. The spider that is mostly mistaken for a False Widow is the very common Missing-sector Orb-weaver, Zygiella x-notata, which is found around the windows of houses in huge numbers. Zygiella doesn’t get to be as big as False Widows can, but since many False Widows encountered are not fully grown, then confusion is inevitable. What Zygiella does is spin a classic spider-web across the front of windows so that insects flying to the windows at night will crash into them and become entangled.. Most orb-weaving spiders spin their webs across fly-ways in the same way that poachers cast nets across rivers. But remember, the False Widows don’t do this because they target different prey. So the dozens of spiders camped around the outside of your window-frames will almost certainly be Zygiella and not False Widow. But they have a very similar body-shape and markings on the back can be superficially similar. Zygiella is usually much brighter and tends to have a silvery appearance.

On the other hand, the male Steatoda grossa False Widow, which has been recorded in Ireland since the late 19th century, can be mistaken for a House Spider, as it has very long legs and tends to scuttle along the ground and will enter houses simply by walking into them, and in this manner is extremely different to the more robust-looking Steatoda nobilis male. Unlike the females, they are not known to bite, but these spiders can get quite large (about as big as a mediu-sized House Spider)  and will frighten most people. The markings on the abdomen have a checker-board appearance like the classic markings of the female.

A large male Steatoda grossa (the smaller of the two large False Widow species found in Ireland). This spider prefers to scuttle rather than climb and can easily be mistaken for a House Spider when first seen.

A good treatment for False Widow venom

Ireland, like most of Europe has become home for species of spiders that can be venomous to human beings. Almost all spiders can potentially bite because all use venomous fangs to subdue prey, and sometimes defend themselves, but False Widows have a venom that has a bigger effect on people.

There are two species known in Ireland and both are believed to have originated in the Canary Islands and/or the nearby island of Madeira. However, these islands were stop-off points for trading ships travelling around the world in the Age of Discovery, from the 1480s onwards for ships rounding Africa or travelling to the Americans, so there is a small possibility they might actually have originated from elsewhere, but a this stage it’s highly likely we’ll never know for sure.


An average-size adult Steatoda grossa of the black variety, although the classically marked variety is beautiful by comparison. This spider looks very like a Black Widow or Australian Red-back Spider. However, none of these spiders is naturally aggressive and can be handled without biting, but care should always be taken.

Steatoda grossa, the smaller one, was first recorded in southern Ireland (and southern England) in the 1870s. Here is was largely confined for over a century but gradually spread northwards. Much later, in the early 1990s the larger Steatoda nobilis appeared, and it has spread all over the east coast and into the midlands now, where it is a very common species. False Widows are so-called because there are many species and most are completely harmless to humans, but they look almost identical to the true Widow spiders, the Latrodectids, such as the Black Widows, Brown Widow, White Widow, Australian Red-back Spider and New Zealand Katipo. There are actually MANY species and several are found in Europe, but not naturally in the British Isles or Scandinavia.

The irony is that of all the False Widow Spiders the two that have arrived in Britain and Ireland ARE mildly venomous to humans. But they are NOT aggressive spiders in any sense, and mostly like to be outside, although they do get into sheds and houses which do not have regular cleaning routines.

The venom of False Widows and Black Widows is a type of acid, so I hypothesised that cures and treatments used successfully on other acidic toxins, such as bee stings or nettles should also work with some degree of success on False Widow venom. Recently a friend was bitten by a small Steatoda grossa. The sting was quite powerful, but I’m happy to announce that treatment of the bite with crushed Dock leaf worked brilliantly and with almost immediate effect.

A leaf of Broad-leaved Dock photographed today...works great on nettle stings and False Widow bites. It SHOULD work on Black Widow bites too, as the venom is very close to that of False Widows. Baking Soda might work even better, but I haven't tested it yet.

Dock leaves can still be found outdoors in Ireland, but the frosts are starting to damage them. However, ordinary baking soda should also work to counteract the acid. HOWEVER, the Ph Balance in all human skin varies, so be careful as there are some people who could find their skin has a reaction to Baking Soda and to a lesser extent, Dock plants, although I’ve never encountered anyone with such problems. Paradoxically people who do have more acidic skin Ph will probably not suffer quite so much from acidic venom on their skin.

Always try treatments a little at a time, unless the pain is severe.

I plan to write more about False Widows soon, to help make identification easier, but there are few native Irish species like them. But do not be too worried because they are mainly outdoor spiders and the venom is not dangerous in its own right. The danger is that it could cause symptoms like other, more serious ailments. Mild muscle cramps in an area near the chest could cause someone with a heart problem, or their medic, to think they were in danger of cardiac arrest, so always record a bite or sting if you suffer one from any animal or plant no matter where in the world you happen to be when you suffer it.