Spiders No.22 – Plumose Hairs.

[Walter Piorkowski]

Leitz Ortholux microscope
4X Leitz projection eyepiece plus 1/3x relay lens

Image No.1
169 images at 5 micron increments
Nikon 10x Achromat objective
Diffused Fiber Optic Illumination

Image No.2
67 images at 5 micron increments
Nikon 10x Achromat objective
Cropped image.
Diffused Fiber Optic Illumination

Image No.3
62 images at .001 inch increments
Leitz UO 6.5 X Achromat ULTROPAK objective
Diffused Fiber Optic Illumination

Canon 50D
Zerene and Photoshop processing.


As if some spiders weren’t hairy enough, this grass spider Genus Agelenopsis is blanketed with fine plumose hairs. They appear as fine fir tree like features seen amongst the spine like hairs. The images above are a, millimeter or so wide, section of the tibia leg member of Agelenopsis pennsylvanica. I don’t know if these are unique to this genus or not. As small as they are, about 36X magnification is needed to see them, they are missed using even a loupe.

The plumose hairs are found on the legs and elsewhere, even on the abdomen. If you care to look at my earlier post, Spiders No. 21, this is the same spider and more plumose hairs are faintly visible there. You can see them in the darker shaded area in the upper right section of the lower image.

Walt

[rjlittlefield]

As if some spiders weren’t hairy enough, this grass spider Genus Agelenopsis is blanketed with fine plumose hairs. They appear as fine fir tree like features seen amongst the spine like hairs. The images above are a, millimeter or so wide, section of the tibia leg member of Agelenopsis pennsylvanica. I don’t know if these are unique to this genus or not. As small as they are, about 36X magnification is needed to see them, they are missed using even a loupe.

Very nicely photographed!

I don't know how widespread these hairs are, but they are certainly not unique to Agelenopsis. I was surprised when I first saw them on a pedipalp I shot a couple of years ago (HERE). Regarding that specimen, Rod Crawford at the University of Washington wrote that:

... it's Hololena nedra, a native species that's a common to abundant house spider in some eastern Washington cities. Same family as Tegenaria, and both have the feathery hairs.

--Rik

[Mitch640]

I love your images. They always leave me with more questions than I might have had before. It looks like someone has cut some of the trees down in #2 and left those smooth stumps. I wonder what that's about. And how does hair grow on chitin anyway?

[Walter Piorkowski]

Boy Rik, what a remarkable match in shape and number of "branches". Maybe someone knows their purpose.

Thanks Mitch. You noticed that bare spot too! Not many lumber jacks in those woods. But seriously, I figured the lack of plumose and other hairs would be from scapeing up against something. However the stumps are so flat. If it was a scrape you would expect a partial hair or a tore opened folical. I suspect that there is a purpose for those stumps, we don't understand. Or maybe the larger hairs snap off at that location ???

Walt