Yes, there are spiders in Ireland. These arachnids are a widespread and established part of the country’s fauna. While the presence of spiders is certain, the question of their danger level naturally arises, especially when an unfamiliar creature is encountered indoors.
The Definitive Answer: Yes, and How Many
Ireland is home to a substantial number of spider species, with estimates suggesting the presence of over 400 distinct types across the island. The overwhelming majority of these spiders are small, native, and rarely noticed by humans, preferring to live discreetly in fields, hedgerows, and forests. They represent a significant component of the local ecosystem, serving as beneficial predators that help control insect populations, which is particularly important in keeping flying and biting insect numbers in check across both rural and urban environments. Only a small fraction of these species ever venture into human dwellings, and these native species are not considered a threat to people.
Common Species Encountered
The spiders most commonly seen inside Irish homes are those seeking shelter during the cooler months. One of the most noticeable is the Giant House Spider, belonging to the Eratigena genus, which is known for its impressive size and speed. Males of this species can have a leg span reaching up to 75 millimeters, and they are frequently seen running across floors in the autumn as they search for mates. These large, brown spiders construct sheet-like webs, often tucked away in dark corners, garages, or behind furniture.
Another frequent indoor resident is the Cellar Spider (Pholcus phalangioides), commonly mistaken for a “daddy long-legs” due to its extremely thin, long legs. This pale spider builds loose, messy webs in basements, ceilings, and quiet corners, where it actively hunts other insects, including other spiders.
Outside in gardens, the Cross Orb-weaver (Araneus diadematus) is a familiar sight, identifiable by the distinct cross-shaped pattern of white spots on its rounded abdomen. This species creates the classic, intricate spiral webs.
Are They Dangerous? Addressing Safety Concerns
Native species possess venom that is not medically significant. The safety concern for most people centers on the False Widow spider, specifically the Noble False Widow (Steatoda nobilis). This invasive species is characterized by a shiny, bulbous, dark brown or black abdomen that often features distinct pale or cream-colored markings. It is now considered the most medically significant spider in the country.
A bite from a False Widow spider, while rare and usually only occurring when the spider is accidentally squeezed or trapped against the skin, can cause symptoms more severe than a typical insect sting. Victims often report localized pain, swelling, and redness, with some cases involving blistering at the bite site or general malaise lasting a few days.
Its venom contains components similar to those in the Black Widow, though in much lower concentrations. Despite its reputation, a False Widow bite is not fatal, and the risk of a severe reaction is extremely low.