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Welcome to our general Forum page.  Please feel free to post a comment on any issue or topic area. If you upload a picture, it will be available for you to insert here with your post. IF YOU WANT HELP WITH IDENTIFICATION, PLEASE PROVIDE A FULL POSTCODE OR GRID REFERENCE AND DATE of the record in your post so that it can be added to the recording scheme. You will need to register and be logged-on to post to the forum. Find out more

Sun 19th November 2017 11:44 by Donald Hobern
Re: ? Tmeticus affinis from Walton-on-the-Naze
Many thanks, Peter.

I confess that I am still a serious beginner with spiders. 

I worked my way through the key to Linyphiidae (https://araneae.unibe.ch/genkey/25/Linyphiidae link) at araneae.unibe.ch and can see I went wrong in my estimate of the position of the Tm1 trichobothrium.  I think that was because I included the length of the joint with the tibia as part of the metatarsus length, which led me down the other branch from couplet 8.  That led me to T. affinis.

I also tried the matrix key (https://araneae.unibe.ch/matrixlinkey link) on the same site, but my prosoma measurement of 1.1 mm excluded G. dentatum and I ended up with a set from which T. affinis was also the only choice that looked plausible.

I was not satisfied that the epigyne matched T. affinis (although it looked closer than many other species), but I did not see any plausible species that I thought matched better at https://arachno.piwigo.com/index?/category/455-linyphiidae link.  I think that in my scan of this page, I was mentally focussed too much on the blackish curved margins at the posterior end in my photos of the epigyne.  I can now see that G. dentatum is indeed a good match.

I was unsure whether the problem was my rank inexperience at interpreting spider genitalia or that I was way off the mark. 

Thanks again for all the help.  Off to correct my errors.

I'm living in Denmark and was just visiting my childhood natural history haunts for a few days earlier in the month (https://www.inaturalist.org/observations?user_id=dhobern&on=2017-11-05 link)

Very best wishes,

Donald Hobern

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Sun 19th November 2017 10:50 by Peter Harvey
Re: ? Tmeticus affinis from Walton-on-the-Naze
This is Gnathnonarium dentatum, a wetland linyphiid spider (as is Tmeticus, a much more diffilcult species to identify, requiring tibial spine and trichobothria Tm1 position information). Not sure why you are seeing Tmeticus affinis in your very good epigyne photo at iNaturalist link

The recording scheme and Essex would request the records resulting from any spider work you do, as long as there are voucher specimens which can confirm any doubtful ids.

Peter Harvey, National Organiser and Essex Area Organiser

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Sat 18th November 2017 17:56 by Donald Hobern
? Tmeticus affinis from Walton-on-the-Naze
I've uploaded some pictures of a female spider I extracted from grass at the edge of saltmarsh in Walton-on-the-Naze (TM262247) to iNaturalist: https://www.inaturalist.org/observations/8849339

I'm a relative novice with spiders but have spent some time keying this out (and realise that it would help if I actually dissected the epigyne, but I'm short on equipment where I am).

I keep arriving at Tmeticus affinis and wondered whether anyone could take a look and tell me if I am completely off track ...  This does not seem to have been commonly recorded in Essex, which makes me assume I'm more likely to be wrong than right.

Many thanks in advance for any help.

Donald Hobern

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