Spider. House. Mystery

[MattPrince]

Originally Posted by No.9 Spider

No problem Matt, A. fenestralis/similis can often be difficult to distinguish by eye though with certain specimens can be fairly obvious if you've had a bit of experience. I'm quite confident that the specimen is A. fenestralis, mainly due to the sharp and dark appearance of the cardiac mark, with no evidence of a lighter line through it along the median line.
The paler median line that splits the cardiac mark can be quite obvious in some specimens of A. similis, though as I say there are many that fall between the two.

Thank you No. 9 - I'll bear that in mind, next time I encounter one.

As for the name - I guess it was the original that was wrongly named, we know that Stroem didn't know he was dealing with two species,he couldn't know his type specimen was the "wrong" one when he named it fenestralis. When Blackwall found there was two species, and probably realised that the new specimen was more likely to occur around windows, he couldn't do anything about it, and simply named his new type similar - similis