Neon tarsus...?

[Transylvania]

This is probably a stupid question but I've been rather curious for a while... I've seen a bunch of pictures of T tarsus and more often than not, I see a bluish-green neon tinge on the pads of their "feet." Is it a special sticking mechanism to help them on vertical surfaces, is it something else, or is it nothing? Just curious. ^^
(Go to this thread and look at the tarsus of the p.murinus, c.huahini, a.metallica, h.lividum, etc.)

 

[cacoseraph]

i believe it is an optical effect that is like, an unintentional effect of the molecular adhesion principles that t's, in part, glasswalk with

molecular adhesion has to have very smooth surfaces to work. smooth surfaces do kooky stuff to light sometimes

 

[Transylvania]

i believe it is an optical effect that is like, an unintentional effect of the molecular adhesion principles that t's, in part, glasswalk with

molecular adhesion has to have very smooth surfaces to work. smooth surfaces do kooky stuff to light sometimes

Ahh okay. Interesting.

 

[moose35]

i think its just the way the pads refract the light similar to a prism.
thats just my $0.01 worth
tom

 

[DrAce]

Diffraction Gratings

As far as I am aware, the effect is one resulting from the pads on the bottom of the tarsus. Essentially, Tarantulas grip surfaces like glass using thousands of tiny ridges, in a similar way to geckos (but much much finer). I can't recall if this is a result of hairs, or actual grooves, but the effect is the same. That's one reason why it's more dramatic on the aboreals - adapted for gripping and climbing.

If you have a regular array of very small grooves, then light will reflect off them and interfere with itself, causing what is called an 'interferance pattern'. In the case of white light, the exact distance between those grooves will leave you with a rainbow light effect, particularly if the surface isn't flat, but is gently curved (making the distance between those grooves slightly variable...).

The best every-day example I can think of is a CD. It has that rainbow-effect if you look at light off it. This is because of the rows of little holes on it. Morpheus butterfly wings (those irridescent ones from S. America) have the same effect - with some extra pigmentation for colour.

The same effect is seen on the tarantula tarsus. Wikipedia has a great set of explainations of it... look up "diffraction", and "diffraction gratings".

 

[elyanalyous]

it is just light reflecting off of the microscopic hairs on the feet. BTW according to my entmology teacher, the tarsa (plural of tarsal claws) are the small claws on the tips of the feet, not actually the feet themselves.

 

[DrAce]

Reflections

It's NOT just a reflection. It's most definately diffraction. Reflected light is part of that process, but it is most definately more complicated than 'just reflection'.

Sorry if that sounds unduely harsh. It's not meant to be... just that I'm 110 % confident about it.

 

[elyanalyous]

Oops your right:8o i ment to type reflection and diffraction of light off of the hairs... I was in a rush when i saw the post and wanted to answer it before i left for my appointment. I rushed to answer it, because of the mis-labeled area of the tarsal claws and the fact that it is hairs. Thank you for correcting me Dr.Ace

 

[DrAce]

Yeah, sorry... reading my second reply sounds a bit nasty...

 

[Nerri1029]

As far as I am aware, the effect is one resulting from the pads on the bottom of the tarsus. Essentially, Tarantulas grip surfaces like glass using thousands of tiny ridges, in a similar way to geckos (but much much finer). I can't recall if this is a result of hairs, or actual grooves, but the effect is the same. That's one reason why it's more dramatic on the aboreals - adapted for gripping and climbing.

If you have a regular array of very small grooves, then light will reflect off them and interfere with itself, causing what is called an 'interferance pattern'. In the case of white light, the exact distance between those grooves will leave you with a rainbow light effect, particularly if the surface isn't flat, but is gently curved (making the distance between those grooves slightly variable...).

The best every-day example I can think of is a CD. It has that rainbow-effect if you look at light off it. This is because of the rows of little holes on it. Morpheus butterfly wings (those irridescent ones from S. America) have the same effect - with some extra pigmentation for colour.

The same effect is seen on the tarantula tarsus. Wikipedia has a great set of explainations of it... look up "diffraction", and "diffraction gratings".

Very nicely done

like the signature too.

I've noticed this effect MUCH more prominently on my P. murinus, H. maculata and my S. calceatum

If I remember correctly it won;t work under monochromatic light.. right?

 

[DrAce]

If you have a monochromatic light (and it would really have to be monochromatic) then you should see light and dark patches. The light will all be a single wavelength, cancelling in places, and re-inforcing in others.

You get the rainbow pattern because single colours get knocked out with a white light.

 

[Nerri1029]

If you have a monochromatic light (and it would really have to be monochromatic) then you should see light and dark patches. The light will all be a single wavelength, cancelling in places, and re-inforcing in others.

You get the rainbow pattern because single colours get knocked out with a white light.

right you'd get the striped suit on 70's TV effect with monochromatic light.

 

[DrAce]

Well, in an ideal world you'd get stripes... but on a curved imperfect tarantula foot, I'd have thought patches... But in principle, it's the same thing, yeah.