Dysdera crocata, the Woodlouse Spider

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rjlittlefield
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Dysdera crocata, the Woodlouse Spider

Post by rjlittlefield »

Let's start with the images.

Image

Crossed-eye stereos...

Image

A closer view of the pedipalp:
Image

Background info is that this specimen came to me in a pill bottle from my veterinarian's reception area.

The folks there had found it creeping around the floor, recognized only that "it wasn't anything like we have had before in here", and wondered if I could help out.

It took a while but I finally tracked down what I think is a solid ID.

The beast is Dysdera crocata, the "Woodlouse Spider" or "Woodlouse Hunter" because of its common prey. Wikipedia has an article on it: https://en.wikipedia.org/wiki/Woodlouse_spider . The map there seems a little out of date, since other sources say that this spider thrives all along the west coast, British Columbia to California. Bugguide.com has quite a few pictures of the beast, for example https://bugguide.net/node/view/1568301/bgimage which shows the distinctive pedipalp, and many more images beginning at https://bugguide.net/node/view/3387/bgimage .

Specific features relative to the ID include six eyes in a tight grouping, four (versus the more common two) respiratory slits on the underside of the abdomen (not shown here), gigantic chelicerae (jaws), and a distinctive structure for the pedipalps (male sex organs -- highly modified mouthparts).

This species is considered innocuous to humans. Its jaws are large enough to deliver a painful bite, with possible swelling and itching, but the toxin doesn't work on people.

Photographic info: Illumination by two Ikea Jansjö lamps diffused through two-ply Kleenex tissue. Nikon D800E, full frame mode, large fine JPEG (36 megapixels). 50 mm f/2.8 Schneider-Kreuznach Componon S, reversed, at the half-stop between f/4 and f/5.6. Magnification on sensor about 3X, uncropped field width 11.55 mm. Area shown in first image is about 8.7 mm wide. Focus stacked from 205 frames, 0.05 mm step size. The first image is done by Zerene Stacker Batch > Slabbing at 10 frames/slab using PMax, followed by DMap of the slab outputs and minimal retouching from PMax to remove halos. The stereo pairs are effectively +-2.2%, made by PMax from the original source images, every 3rd frame. Stereo cropping by StereoPhoto Maker.

I hope something in here is interesting!

--Rik

Edit: URL glitch

MarkSturtevant
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Re: Dysdera crocata, the Woodlouse Spider

Post by MarkSturtevant »

Great pictures! One of my many wishes is to run into one of these. They use their big jaws to flip over wood lice / pill bugs -- whatever you want to call them.
Mark Sturtevant
Dept. of Still Waters

NikonUser
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Re: Dysdera crocata, the Woodlouse Spider

Post by NikonUser »

Interesting.
My text says they 'like' living with us - synanthropic (I had to look it up !).
18 months to mature and then live up to an additional 3 years
NU.
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.

Nikon camera, lenses and objectives
Olympus microscope and objectives

lothman
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Re: Dysdera crocata, the Woodlouse Spider

Post by lothman »

great 3D effect.

Rik since you often show such excellent examples. I would like to have a small (mostly mechanical) viewer and print such 3d stacks on something like postcard size to have a stack of cards for viewing. Crossview does not work for eveybody and is somehow stressing for the eyes.

Have you ever tried something like this:

http://www.loreography.net/pages/produc ... photo.html

http://www.loreo.com/pages/products/lor ... iewer.html

http://www.loreo.com/pages/products/lor ... photo.html

https://www.berezin.com/3d/wheatstone.htm

or can you recommend another product?

rjlittlefield
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Re: Dysdera crocata, the Woodlouse Spider

Post by rjlittlefield »

lothman wrote:
Thu Jul 23, 2020 5:59 am
Have you ever tried something like this:
...
or can you recommend another product?
When I go to conferences, I take stereo prints on 8.5 x 11 inch glossy paper, in parallel layout, and several of these viewers:
https://www.berezin.com/3d/pocket_3dvu.htm

I also have some of the https://www.berezin.com/3d/wheatstone.htm . They work OK too, some units better than others. The wrinkle is that some of the optics have changed over the years (lens power and darkening). I am not sure exactly what the current units are.

I used to use https://www.berezin.com/3d/3d_scope.htm and was sad to see those discontinued.

I expect that for a card-sized print, any of the parallel viewers with just lenses would be OK.

But for any other size I am deeply suspicious of lens-only viewers because of the prism effect discussed at viewtopic.php?f=25&t=29932 .
Crossview does not work for eveybody and is somehow stressing for the eyes.
My wife is totally unable to use crossview but loves stereo. To let her see, I use one or another of the Berezin mirror-based viewers and swap crossview images to parallel in StereoPhoto Maker.

--Rik

lothman
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Re: Dysdera crocata, the Woodlouse Spider

Post by lothman »

Thanks Rik,

so I will havet o do a search for an European distributor, since shipping from US is slow these days.

best regards
Lothar

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