Possible to ID spider from shed skin?

[mbaldw]

Hi folks,

we found the below shed skin of a spider on our bathroom window ledge earlier in the week and wondered whether it was possible to get an indication as to the type of spider (Family or possibly Genus?) from which it came? I suspect the answer is no, but I'm curious nonetheless. The scale is centimetres.

Cheers,
Marc.

[MattPrince]

Most likely candidate would be a house spide tegeneria (going on size, habitat and structure).

There is a minute set of hairs on house spiders (and other related speices) at the end of each leg, that would be very difficult to see, even on your crystal clear photo's - not sure if they would be visible on the shed skin, but you'd need a hand lens to look for them, even so, can be difficult to see. A very fine set of erect hairs that get bigger as they approach the end of the final leg joint! Try googling "trichobothria" for an example like this one

Cheers,
Matt

[mbaldw]

That's great - thanks very much Matt. I still have the skin, so I'll take a look with my USB microscope and see if I can spot the hairs.

Cheers,
Marc.

[MattPrince]

That is cool - in which case, they are on the top surface of the final tarsal segments and you might want to try varying the colour of the background. They should be visible at x10 or above, its a question of getting the light on them correctly - and higher magnification with a limited plane of focus might make that trickier.

You'll know you have them if you see a line of fine erect hairs that gradually increase in length as they approach the tip of the tarsus.

They are interesting in that they are part of an agelenids "spider sense" with which it can detect air movements from nearby prey.

By coincidence last night I was called by my landlady to deal with a house spider and I'm now in possession of a fair sized live tegeneria male (presumed duellica from size alone), currently lurking in an old laphroig cannister, once I get home I'll see if I can coax him into a couple of pictures.

Cheers,
Matt

[mbaldw]

Fascinating stuff, thanks Matt. I had a quick(ish) look with the USB microscope and there's so much hair that I can't make out the set you refer to. I never realised how much hair spiders had, or the apparently different size and thicknesses. I presume these have a sensory function too? I also never noticed the tarsal claws, which look pretty awesome. This has inspired me to pick up the copy of Foelix's Biology of Spiders that's been sitting on my bookshelf for over a year I thought I'd share some of the pics, despite them being fairly poor quality, as I thought they were cool:







Thanks again.
Cheers,
Marc.

[MattPrince]

Nice stuff Marc, however I'm beginning to think the trichobothria don't persist with the shed skin - a couple of your pictures would probably show them up, even though they are hellishly difficult to see. I've just had a lot of fun trying to photograph them on my large live tegeneria sp. The angle and depth of focus are pretty critical, I found a x30 was the best to see them in the end, using a field microscope with poor spider entrapped in a clear poly bag. Sadly I couldn't digiscope it though (as I'd like to have done with the palps for species id).

Nice shots of the tarsal claws btw (pics 1 & 5). If the trichobothria were to show up I'd have hoped to see them in shots 3,6 or 7 as a row of isolated erect hairs, generally increasing in length towards the tarsal apex. The fact that there aren't many internet pictures atests to how hard they are to photograph!

This is the clearest representation of this feature I can
find. They are so fine that focus is critical, even with a hand lens!

All the best,
Matt