Harvestman with white rump

[Bruce Williams]

Stockgrove Country Park, Beds. This afternoon (21st December 2008).

Help with id appreciated.



Bruce

[Geoff F]

Firstly, I would recommend reading Arp's detailed reply to a similar recent question Harvestman

Based on the trident assembly and eyes together with what would appear to be square sided femora I would suggest Oligolophus tridens.

But the femora can be misleading in photos as colouration can make them appear angular when they are actually round. While the trident is a general good guide considerable variation can occur. It is also a bit late for tridens although it has been a mild winter so far.

Therefore my second choice would be Paroligolophus agrestis with Arp's other suggestions taking third place.

ps. This is the ID site which I recommended in the earlier question, see what you think. (Site originally suggested by Arp. I have found it very useful). http://www.spiderling.de/arages/Foto...ens_7_1024.jpg

[Geoff F]

One other point. If you, Bruce, or anyone else is interested in seriously learning about Harvestmen I recommend reading Action Man's article • View topic - British Harvestmen

This excellent work has become my chief source of reference and I frequently refer back to it.

[Bruce Williams]

Thanks for your advice and the excellent links - much appreciated.

I had followed Janet's harvestman thread for quite a few postings, however, obviously not long enough as I'd missed Arp's post - informative as always.

I was quite intrigued by the markings on this specimen. I know they can be very variable but I thought this one was quite striking with it's white "rump". A few weeks ago I came across two harvestmen that had a lot more white on them (same location different fence). I'm pretty sure they were the same species - here one of the pics:



Bruce

[Pudding4brains]

Hi2all,

No time for lengthy answer at the mo, sorry.

The beast in the top image is Oligolophus hanseni (female) - just the right time of year for her too.

The differences with tridens are very subtle and it's only thanks to the excellent photo quality of Bruce's image (as always) that I dare to put a name to it.

Most striking difference is in the trident:

O. hanseni: Trident inclined more forward, usually with accessory tubercles left and right of the trident and some random tubercles behind it. Ocularium somewhat inclined backward, usually darkish with 2 rows of distinctly recognizable usually clear coloured tubercles, slightly diverging toward the rear.

O. tridens: Trident inclined more vertically upward, usually quite 'cleanly' placed without clear accessory tubercles to the left and right and only few and feeble ones behind (if any). Ocularium straight up, usually clear coloured with 2 rows of distinctly recognizable tubercles in the same colour, evenly spread front to rear.

Like Geoff mentioned, most authors also distinguish angular femora (tridens) and rounded femora (hanseni & agrestis), but I have a genuinely hard time recognizing these on photos as the rounded femora will have rows of hairs/spines that imho make them look angular way too much on most photos

With the second animal Bruce posted I wouldn't want to make a bold statement as to the species name. It's very probably the same species (the trident seems to have the accessory tubercles), but what throws me is the colouration of the ocularium - more tridens like With my current recognition skills I would best need a slightly better zoom/crop of the ocularium and trident area ... sorry.

Nice to see Geoff pass on the links to my favourite Opiliones-sites (no need to always repeat that I suggested them though - I probably only found them through tips from others too ). Please be aware that Action_Man's article on "British Harvestmen" is still undergoing corrections, rewrite and extensions - so, over the coming months, do check back for enhancements. It is also rumoured that (at some point) there will be a PDF version available

Cheers, Arp

[JRsbugs]

You have a very nicely detailed pic there Bruce, even if it does have a white rump!

Thanks Geoff for the link to Action Man's article too, and thanks to him for writing it. Next time I find a harvestman/woman, and if I can see it well enough, I will be studying those notes!

I have noticed a theme with your bugs Bruce, you also had a spider with quite a white rump! Must be something they are eating.

Janet

[JRsbugs]

Good to see you back Pudding!

[Action_Man]

Nice finds Bruce, and captures.

You can see how dangerous it is to guess the species on these little devils, i did have the 1st down for tridens, on the key for the tridents, tridens and hanseni are pretty similar, with hanseni having three small additional spines above, you need a pretty good picture to see these, like the ones in this thread.

I need to have a look at updating that tridents key ...

[Bruce Williams]

Arp -Thanks for a very helpful and interesting interesting post. As to pic2, well unfortunately it was taken with my Canon A650 compact camera and that's as big and as detailed as it gets . I have already added Gordon's "British Harvestmen" website to my Favorites and as I'm a big fan of these fascinating creatures I'm sure I'll be a regular visitor to the site.

Janet - Thanks for your comments .

Gordon - Thanks for your comments and my respect for your excellent work on a very worthwhile resource.

Bruce