I arrived at band practice last night to discover that our drummer had just violently ejected a spider from his bass drum, on the grounds that it looked like a terrifying false widow. Full marks to him for the ID, as it is indeed a Steatoda. I think it is S. grossa, but the online illustrations of the epigynes show S. nobilis as having a rather similar epigyne, so I'd appreciate any opinions on this one. There is a bump in the anterior edge that may suggest nobilis, but otherwise it looks more like grossa to me. The spider is a little squashed, but is about 9mm long, so falls within the lower end of the range for nobilis, and towards the top end for grossa. Thanks.
These are one of the few occasions when its generally easier to id on abdomen pattern than epigyne as the differences aren't glaringly obvious.
Its difficult to be sure from a single photograph ( I was discussing this with Malcom Storey over email recently - it would be great to have 3d rocking images rather than flat 2d ones) which is why all the real experts tend to insist on the specimen - however, - I would agree with you - this looks more like s.grossa than s.nobilis. The septum in this photograph appears to be slighly fluted, and not as broad and plain as typical s.nobilis. Both spiders can have a lip on the lower edge, so that's not a problem.
Another indicator to s.grossa would be if the abdomen is unpatterned and the colour of a particularly heft italian red wine.. old grossa seem to get like that, I'm sure that s.nobilis can turn up unpatterned but I've yet to find one without any trace of a patter, or at least a scarf.
Not an absolute id, but I hope that helps!
Regards,
Matt
Thanks Matt - the abdomen was a mottled purple/brown, with no trace of white lines or spots, and I agree that the septum on the actual spider looks narrow and fluted. There is a lip on the lower edge, but also a small rounded tooth on the upper edge that I couldn't see in any of the illustrations for grossa. But it does seem to fit grossa on the majority of characters.
No probs Martin,
All fits with mature female s.grossa.
Cheers,
Matt