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Can anyone identify this spider that I have just found in my home?

enter image description here enter image description here

Details:

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  • $\begingroup$ Are those ice crystals in the photo? I'm curious as to what surface the spider is on, seems almost like the windshield of a car. $\endgroup$
    – Ark Lomas
    Jul 23, 2020 at 20:19
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    $\begingroup$ No, it can't be ice, because it is a middle of summer here, in Poland right now. I found this spider in one of my rooms, captured it gently to some plastic pot and then move it to a windowsill beyond one of my windows, where it was released. These marks you spotted are microfractures in the windowsill itself. It seems, it was painted with using a fairly cheap paint, since in went into this condition in less then 10 years of a moderate weather conditions, we have here. $\endgroup$
    – trejder
    Jul 24, 2020 at 19:13

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It is a Barn Funnel Weaver (Tegenaria domestica), In Europe it is known as the domestic house spider.

Here's some photos of this species to prove the similarities: enter image description here enter image description here

What caught my eye in particular that made it more clear that it was this species was the color patterns on the abdomen and cephalothorax, the size you mentioned, the shape of the feelers as well as the location.

The slight difference in shade of color may be due to being a different variety of the species or simply because of the weather and habitat that the spider is in.

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    $\begingroup$ Thank you! As for the other differences you mention, I can't say anything specific as I am not a arachnology expert by no means. As for the size, I can be completely wrong, because when I came back to measure it, the spider was simply gone. But, I can see at Wikipedia: "Their body/legs ratio is typically 50–60%, which accounts for a body size of 7.5–11.5 mm" whic means, if I am not mistaken, that it has 2 cm at max. The one that I was observing certainly wasn't that small. I think it was more closer to 3 cm. $\endgroup$
    – trejder
    Jul 24, 2020 at 19:10
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    $\begingroup$ barn funnel weavers tend to have banded (striped) legs, while the specimen in question doesn't have banding and so it is likely Eratigena (a genus offshoot of Tegenaria) especially considering the leg length ratios. This is likely a 'giant house spider,' one of the Eratigena species. $\endgroup$
    – JimN
    Aug 25, 2020 at 3:06
  • $\begingroup$ @JimN You raise a fair point, I suggest you make a detailed answer. $\endgroup$
    – Ark Lomas
    Aug 25, 2020 at 20:04
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Most species identifications require a microscopic examination of genitalia, so for many species identifications, a photo is only reliable up to genus level. So I will talk a bit about the genus first. We can, however, rule out some species from the photo...

With the lack of banding in legs, it is unlikely a barn funnel weaver and more likely one of the Giant House Spider species (of the genus Eratigena). Regarding the genus: some sources will equate the Eratigena and Tegenaria genuses with each other, while most separate them with a notable recent change of the hobo spider which used to be Tegenaria agrestis and now considered Eratigena agrestis. Taxonomy is ever-changing. A hobo spider would have two dark stripes running lengthwise on the carapace like the barn funnel weaver, which your specimen does not have. The Carapace marking of giant house spiders can have two dark stripes or a other patterns that look like radial lines emanating from the centre of the carapace.

Whether it is E. atrica, E. duellica, or E. saeva is difficult to tell. They are all known as a 'Giant House Spider' by common name. In north america, one is known to have spread on the east cost and another species on the west coast. But in Europe, I don't think it is as easy to use geography to rule out certain species, so I don't think it is possible to tell which of the Giant house spider species it is.

Here is a photo of a giant house spider: E. atrica, (Observation © kevinindorset)

They darken in colour as they grow in their shell/exoskeleton, and after molting, they are very light coloured (and vulnerable).

The second photo is one believed to be E. saeva: E. saeva (Observation © Paul Bowyer)

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