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False Widow Spiders in Ireland

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What are False Widow Spiders?

Steatoda Nobilis, the “noble false widow”, is thought to have been introduced to Ireland in the 1800s.

During the following 100 years or so they remained quite small in numbers and were mainly confined along the south coast.

But they are now spreading, possibly as a consequence of global warming.

Are False Widow spiders’ Bites Dangerous?

Only a small number of the larger Steatoda species of spider have fangs capable of penetrating human skin.

A number of reports have been made of people being bitten by spiders and false widow spiders are often the focus of this, particularly in the media.

Steatoda nobilis have been implicated in bites on humans, but the bite is almost exclusively of mild effect on humans, without severe consequences that can present from black widow spiders.

It is often alleged that the false widow spiders’ bite is medically significant for humans. However, the few bites that were recorded do not present typically long-lasting effects. The bite symptoms are usually similar to a wasp or bee sting

Complications, if they do arise, are usually associated with secondary infections caused by scratching of the bite etc.

In fact, when one considers the undoubtedly large number of people who are being stung by bees and wasps every year, the risk of a false widow spider bite is surely relatively small. 

For reference, the only alleged severe reaction we are aware of was one where a woman in the UK reported such a reaction, although it was never confirmed that this was due to a false widow and this was way back in 2009.

That is not to say that there is not the possibility of an allergic reaction, but evidence of this is few and far between and we need to keep in mind that a proportionate response should be considered.

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Are False Widows Aggressive?

By nature, false widow spiders are sedentary and remain in their cobwebs. The males are the only ones likely to move around when they become ready to mate. Therefore in order to get bitten, you will probably need to put your hand into a web, handle one roughly or sit on one without realising it.

Reports of false widow bites may be exaggerated by the media and are not easy to substantiate in reality.

In conclusion, getting bitten by a false widow spider is not likely in Ireland in normal circumstances, and the consequences of a bite will most likely be less severe than a bee or wasp sting.

A more serious problem is only likely to arise in the event of an allergic reaction or if other health issues already compromise the person.

Can we do Pest Control Treatments Against False Widows?

Some companies do undertake treatments against false widows, but you need to consider whether this would be effective, especially if carried out in gardens and outdoors, etc. as any insecticide would be very quickly washed away by rain and broken down in sunlight.

Also, any insecticide would be non-selective and therefore kill or adversely affect any other invertebrate life present.

Even if carried out internally, the insecticide would break down and the building would be quickly reoccupied by spiders of any group.

Finally, it is not possible to spray insecticides on walls and ceilings as it will lead to discolouration and damage to paintwork. Carpets and floorboards can also be affected by insecticides.

False Widow Spider Prevention

To prevent spiders around your home we would advise the following:

  • Seal cracks and use screens on doors and windows.
  • Use a vacuum to remove adults, egg sacs and webs. Do not use a broom as adults usually escape.
  • Inspect and seal cracks on the outside of the home, especially around doors and windows, and use screens to prevent home entry.
  • Using yellow-light bulbs for your outdoor lighting may reduce the number of false widow spiders (and other insects), as they are more attracted to sources of white light.
  • Lowering the amount of moisture in cellars, basements and crawl spaces with a dehumidifier or ventilation can discourage cellar spiders’ activity around the house.

None of these recommendations require insecticide or professional treatment but just standard housekeeping and common sense. Deprived of their web, spiders cannot catch their prey and rapidly disappear.

Sometimes a spider egg sac is accidentally brought into a building/apartment without the person being aware (e.g. with a luggage or cardboard box), which could explain why they found several spiders suddenly.

Owl Pest Control does not provide a service for controlling spiders as insecticides are not usually necessary, and will only control activity until the residual insecticide becomes inactive, after 3-4 weeks.

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