spider for id

[MattPrince]

Hello
Found this young female spider in a low bush in a garden in Cambridgeshire whilst looking with my young friend Dominic. We think it is a tetragnatha species.

possibly t.nigrita?
Thanks for looking
Matt and Dominic

[Geoff F]

That looks like two different species there, Matt.

The Tetragnatha family are difficult to identify even from really clear close up photos.

T. nigrita is an uncommon variety so unlikely. I would expect this is more likely to be T. montana which is a common species and can be a bit dark or T. obtusa which is a bit localised but possible.

The other spider appears to possibly be a juvenile, which would make ID even more difficult; although it does have a bit of a look of Linyphiidae about it.

But I would need a lot more details before making a firm suggestion. Perhaps one of our real experts can be more positive.

[MattPrince]

Just the one spider Geoff!

Definately juvenile female, all dark sternum, well away from water with a dark carapace as well as a dark body. Late in the year for any tetragnatha sp. so it was a surprise find when I went spider hunting with a friends young kid.

Cannot be positively id'd but still consider nigrita a possibility..

In any case happy new year!

Matt

[No.9 Spider]

I think the last photo is just taken at a deceptive angle as it appears to shows the chelicerae typical for the Tetragnathidae or 'long jawed orb weavers' ('four jawed' strictly translated. Females can be difficult to i.d. having only a broad 'tongue' projecting from the epigastric fold as opposed to the detailed and often distinct epigynes of many species.
The sternum can be indicative to a degree. A lighter median area on the sternum can be indicative of T. extensa or T. pinicola, whereas a lack of this lighter area applies to all the other Tetragnatha species.

There are only three records for T. nigrita in Devon and it's quite rare so we can only surmise (or rear it to adulthood).

[MattPrince]

Well my track record for rearing spiders isn't very good - so I didn't take it - also would have had to explain why I was taking a specimen for what would ultimately be lethal examination to a 6 year old (some of the tetragnatha need cleared epigynes for conclusive id I seem to recall).

The spider was in Cambridge no 9 - hence, combined with other characters, I considered t. nigrita, though as you and Geoff have pointed out the much commoner t.montana could not be ruled out (don't think t. obtusa ever gets this dark does it?).

Anyway of this group t.pinicola and t.extensa are my favourites - the only ones that are easy to id!

Cheers,
Matt