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What keeps a tarantula from getting caught up in it's own webbing?
Why don't tarantulas get tangled in thier own web?
- Thread starter Ewok
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I am not 100% sure but spiders have glands on their feet that produce oils that keep them from getting stuck to its own web. I assume it is the same for T's
I don't think this is true, I think it is an unsupported hypothesis or just a rumor. I know that it was published in several old books, and is on some websites, but I think it has been overturned.
As for Tarantulas, they do not produce sticky web. On top of this, some do get tangled in their webs, especially my P. regalis, happens to him on occasion.
Many true spiders do not produce sticky web either. They depend soley on flying insects getting tangled when they hit the web. They don't get stuck because they don't fly into their own webs, and special hairs on their tarsi help them to move around the web more effectively.
As for true spiders that do produce sticky web, they also produce non-sticky web, and move around on that. Even then, I have seen some get stuck to their own webs when trying to make a hasty retreat.
More info here: http://www.news.utoronto.ca/bios/askus1.htm
http://www.microscopy-uk.org.uk/mag....microscopy-uk.org.uk/mag/art97b/benspid.html
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yeah okay like I said I wasnt 100% sure.I must have just seen it in a old book or somthing. I have even heard that spiders vibrate thier legs as they walk to stay free. I am not to sure on how true that is but, it would be somthing to watch 
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lucanidae,
do you think that tarantula scopulae act via van der Waals force? since they can climb smooth surfaces like glass, much like geckos...
that's what it seems like to me! but, I don't know if this has been proven or not???
thanks,
Chris
do you think that tarantula scopulae act via van der Waals force? since they can climb smooth surfaces like glass, much like geckos...
that's what it seems like to me! but, I don't know if this has been proven or not???
thanks,
Chris
It's an interesting thought, but I doubt it. Although tarantulas and insects can do amazing tricks like glass walking and hanging upside-down, it is most likely accomplished purely by their tarsal claws and tarsal scopulae. In order for the van der walls force to occur, those hairs would have to subdivide into smaller hair again and again and again, and this is not the case. Looking at SEM pictures of spider and insect tarsi, you just don't see it. Geckos on the other hand, being much heavier on average, need a different system. I believe they use both the van der walls force and some suction effect to accomplish their cieling walking.
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Geckos do not use a suction effect, their ability to climb any smooth surface is accomplished primarily, if not exclusively by van der waals force. There were also theories that capillary action played a role in their ability, but totally dry synthetic copies of gecko bristles have worked effectively. The keratin that gecko bristles are made of is also generally water repellent. Apparently it's purely the mechanical design that allows them to work, by taking advantage of this force of attraction between objects of less than 2 nanometers. There's also an inverse relationship between the weight of the animal, and the density and fineness of the bristles. Tests have shown that a Tokay gecko has enough adhesion in reserve that it would be able to support 120kg if all the contact surface of it's lamella was connected at once, which is why it can move so freely, only using a small amout of it's reserve. An animal like a tarantula could still climb surfaces like glass effectively with much less bristle division, it just wouldn't have as much reserve. Contrary to what you said the hairs would not have to subdivide into smaller hair again and again and again, as long as they fit into the range of 2 nanometers or below to begin with.lucanidae said:
Tarantula adhesion has not been intensively researched as gecko adhesion has, but the people who conducted the gecko research seem to believe that insects and spiders use the same very effective system, I don't understand why you don't. Can you actually believe that the tarsal claws of a tarantula are hooking into the microscopic imperfections on a pane of glass, even when the animal is upside down? When my tarantula climbs the side of the tank, the tarsal claws usually aren't even in contact with the surface. You also say you think it's accomplished by the tarsal scopulae. So what do you think they're doing?
Tarantulas aren't secreting sticky adhesive from the scopulae, they aren't wet. Wouldn't it just be logical to conclude that they also use van der waals force? If you really don't believe this is occuring, how would you explain a tarantula walking upside down on a ceiling, there's no sticky secretions, there's no suction, even if the hairs are hooking imperfections in a surface, how are they staying there without some attractive force? Also, you say you that you just don't see it in SEM pictures of tarsi, but even in this relatively low magnification picture, the bristles appear to thicken at the ends: http://www.astrographics.com/GalleryPrintsIndex/GP2123.html
I'm not saying my argument is 100% right, I'm just going on the reading I've done about the well documented gecko research, and what I've personally observed in spiders, maybe I'll have to study it in detail myself.
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I've seen a juvie S. calceatum get tangled up in its own web. Luckily it wasn't me that had to do the de-tangling
Stewart
Stewart
Never seen a tarantula hang upside down from glass...maybe an arboreal could pull it off....but not easily
Are you sure? They could be excereting a tiny drop of oil onto the hairs, which is carried with the hair when it moves on. It could leave only the tiniest trace behind and still work.
Richard D. Fell, associate professor in the department of entomology at Virginia Polytechnic and State University, adds some other details:
"The segments, or tarsi, at the end of insect legs possess clawlike structures that help the insect hold on to different types of surfaces. These tarsal claws are used to grip the tiny irregularities on rough surfaces. But in some cases, insects do make use of a kind of adhesion. If the surface is smooth, the insect can hold on using the adhesive action of hairs located on sticky pads (known as the arolia or pulvilli) on the tarsi.
"Some insects, such as grasshoppers, have pads on each of their tarsal segments, and some insects may have special adhesive pads on other segments of the leg. The pads typically contain numerous hairs that secrete an oily substance that causes the tips of the hairs to adhere to the surface. This substance provides the traction and stickiness that allows insects to hold on to smooth surfaces, such as glass."
The picture you linked to shows the suction pad, common in flies, and the hairs that will secrete tiny drops of oil.
Considering that tarantulas are much more closely related to insects than geckos, I'm going to go with this professor and not with interaction between the molecules of a tarantula foot and molecules of glass. Ever seen a terrestrial tarantula walk upside down on a smooth ceiling....me neither.
http://www.sciam.com/askexpert_question.cfm?articleID=00053735-601D-1C72-9EB7809EC588F2D7
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Actually, I've seen my Grammastola walk upside down on a smooth "ceiling" regularly, I'd say the lid of a deli cup is just as smooth as anyone's ceiling. Why specify terrestrial though? Are you saying that arboreals and terrestials use a different mechanism to climb? Seeing any species of tarantula walk upside down on a smooth surface should validate the point, unless you believe that arboreal tarantulas are closely related to geckos, and terrestrials are closely related to insects instead. I also haven't seen anything written suggesting that tarantulas secrete a sticky substance, or any other substance from their tarsal pads. We can't assume that their method is exactly the same because some insects do it.lucanidae said:
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Actually, I read this: http://www.amazon.com/gp/product/03...f=pd_bbs_1/103-0936620-1751022?_encoding=UTF8 which covers a good number of other examples of biology inspired engineering as well. I've also kept several species of gecko, including the Tokays I mentioned.Gigus said:
That's what the lid of your deli cup looks like. Not a very smooth surface, especially the crappy plastic they use for deli cups.
I'd have to say that arboreals most likely evolved a climbing ability that was better than terrestrials, I think that's a given. And no, I don't think arboreals are related to geckos, I mean, cmon, why would they eat their cousins right???
Yes, and seeing any human escape from a strait jacket means we all have amazingly pliable joints. One occurence dosen't support anything.
Right, and we can't assume the mechanism is the same just because some geckos do it.
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I know the surface isn't actually "smooth" that's the whole reason behind any animal being able to climb surfaces that appear smooth to our eyes, the fact that they're not. So what's your point? I doubt that your ceiling, or anyone's is much smoother than that surface on a microscopic level. If a terrestrial tarantula can adhere to such a surface while upside down, it only stands to reason that an arboreal can do it even better. Still don't see what the picture was supposed to prove.lucanidae said:
That's what the lid of your deli cup looks like. Not a very smooth surface, especially the crappy plastic they use for deli cups.
That picture shows all the nice places for claws and hairs to grip on. While geckos have been shown to grip onto nearly completely smooth (even at microscopic level) surfaces, as I'm sure you are aware.
As you said:
So all we can do is conjecture. But we do know that both spiders and insects use their claws and sticky tarsal pads and (oily, insects at least) hairs.
Check out an Avic. avic's tarsal pads one day, I'm sure you'll see some cool mechanical action that seems to sugest some sort of suction effect or claw/hairs digging in and being removed.
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Jonathan, you are correct, and look earlier in this thread for support for your idea.
I know that tarantulas have some amazing climbing ability, and that my two trial preliminary test shows..well...nothing.
Try this same test yourself everyone, with arboreals and terrestrials. My guess is, arboreals will fall less, and terrestrials will fall say...I dunno...50 percent of the time...just a random number really, a testable hypothesis in fact.
Now let's do this same test with tokay and related geckos and see how often they loose their grip. My guess is, significantly less than the tarantulas did. This supports the theory that tarantulas have a less powerful mechanism for climbing, and therefore it is unlikely to be van der walls.
I just tried something. I have a sling Holothele sp. "Notre de Santadander" that is really quick. I tipped its vial slightly to allow it to run towards the top, which it did. I then slowly turned the vial to a more vertical position, the sling fell. Either it didn't have the ability to cling to the surface, or it really wanted to fall. Then I tried this with my 1 inch B. vagans, this one didn't run towards the top so I tipped the vial and let him walk about halfway up, then I tipped it slowly back towards vertical, and again he fell.
I know that tarantulas have some amazing climbing ability, and that my two trial preliminary test shows..well...nothing.
Try this same test yourself everyone, with arboreals and terrestrials. My guess is, arboreals will fall less, and terrestrials will fall say...I dunno...50 percent of the time...just a random number really, a testable hypothesis in fact.
Now let's do this same test with tokay and related geckos and see how often they loose their grip. My guess is, significantly less than the tarantulas did. This supports the theory that tarantulas have a less powerful mechanism for climbing, and therefore it is unlikely to be van der walls.
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I think we already covered the fact that the species of tarantula isn't going to effect the method used, I don't know of any species of tarantula that can't climb a smooth vertical surface. Just seems like you're really opposed to the idea that they might use van der waals force. I don't know if they do, but it seems like a logical possibility. Secretions are another logical possibility, but one that's equally unproven for spiders. I explained how the gecko's feet work, which you were obviously unclear on, I just don't know why you would be so opposed to one method just because it's unfamiliar.lucanidae said:
Not opposed, I just don't think that it is right. I've also presented some good arguments for why it isn't right, and some counter ideas that have been shown to work. Your arguments for why it is right have thus far been unconvincing to me, but that dosen't mean that I am unconvincable. The idea isn't unfamiliar, just because I didn't get the mechanics of the van der walls effect usage by geckos exactly right dosen't mean I don't believe that geckos use it, I just don't believe tarantulas and insects use/need it.
Not always the case, look at Tarantula breeding methods. Seems to me that if some have male hooks and some don't, then some could have different tarsal structures than others. Anything is possible. Look at insect tarsal diversity, it is incredibly diverse. Looks at true spider tarsi versus mygalomorph tarsi, even trap door spiders versus arboreal and terrestrail Theraphosidae.
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