Tag Archives: arachnophobia

The Mouse Spider, for those who are worried

A few people have been asking me about the Mouse Spider, following a scary story in the media this week about a British man who was bitten by one which had somehow climbed into his bathrobe. The man had an allergic reaction causing his back to swell up, and it was because of his own knowledge of spiders he was able to identify the spider as a Mouse Spider (Scotophaeus blackwalli). The media went into overdrive, some reporting that the Mouse Spider is a close relative of the deadly Australian Sydney Funnel-web spider. This is a mistake – there are a number of species of spider in Australia known as Mouse Spiders, and they are related to the Sydney Funnel-web, but they are no relation to the much smaller European Mouse Spider. Here is a photo I managed to take of the European Mouse Spider in May 2015 – I haven’t seen one since then:

The common name for this species comes from the fact it has mouse-coloured hair on its abdomen – it is nowhere near as large as a mouse, and, in fact, appears quite a bit smaller than the so-called Giant House Spider (Eratigena atrica) which terrifies so many people in the autumn, when big long-legged males enter houses cruising for females. Here is one of these harmless terrors I photographed a few weeks ago:

The Mouse Spider is a stocky, slow-moving spider which is native to Northern Europe, including the British Isles, and widespread but very rarely encountered by ordinary householders. It tends to like bark and stones to live under, and will wander around at night, hunting small invertebrates by sneaking up on them. The female has a reputation for biting if handled, but it is a shy species and definitely doesn’t go looking for trouble. The body of the female would be about as large as the body of a female Giant House Spider, but the legs are far shorter and it is, in many ways, more handsome. The bites are usually harmless although definitely noteworthy, but an allergic reaction is always possible with any creature capable of biting or stinging.

The best way of keeping spiders out of your house is to not leave doors open at night, in the morning or approaching darkness, and to check outside before opening windows. Also, do clean your home regularly to prevent them making themselves comfortable.

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.