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#1
Old 12-11-2006, 10:07 AM
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How do spiders know how to build webs?

Building a web is a complicated business, involving an intricate series of inter-connected stages. How does a spider know what to do?

It doesn't learn the pattern or 'blueprint' from previous examples, or from its parents.

Is the 'knowledge' inherited? I thought that only genes are inherited, and genes are codes for how to build the proteins that build the cells that build the creature. They don't contain 'blueprints' for webs.

So... how?
#2
Old 12-11-2006, 10:18 AM
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The same way that birds know how to build nests, they just know
#3
Old 12-11-2006, 10:21 AM
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Quote:
Originally Posted by ianzin
Is the 'knowledge' inherited? I thought that only genes are inherited, and genes are codes for how to build the proteins that build the cells that build the creature. They don't contain 'blueprints' for webs.
Why couldn't they? They contain the information necessary not only to provoke the formation of body parts, but to arrange them into the right places, so why not, say, arranging neurons into the specific configuration necessary to provoke or enable a certain kind of behaviour or data processing.

Spiders' ability to build webs is information, but so is the arrangement of stripes on a zebra.
#4
Old 12-11-2006, 10:28 AM
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Quote:
Originally Posted by ianzin
I thought that only genes are inherited, and genes are codes for how to build the proteins that build the cells that build the creature. They don't contain 'blueprints' for webs.
According to some twin studies, they seem to also contain family names, mannerisms, and habits. Seems twins brought up in different homes end up marrying women with the same names or drinking their coffee exactly the same way or sharing many mannerisms that are peculiar to them. So if that can be inherited, then so can spiderweb-making.

If you think of it, how does any creature know anything? Why will pandas only eat eucalyptus? There's a whole dang forest out there; nothing's stopping them from munching down on any other leaf or tree or even chomping a snake but they don't.
#5
Old 12-11-2006, 10:33 AM
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It would be amazing if spiders actually did learn to build webs. Seems that would be more amazing and require greater "brain power" than inherited interaction patters with the environment. Of course, birds that grow up not hearing their species sing, IIRC from some anicent PBS tv show, don't sing "as well" as those that grow up hearing mom and dad, etc. So there's an interaction.
#6
Old 12-11-2006, 10:33 AM
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Quote:
Originally Posted by Quiddity Glomfuster
Why will pandas only eat eucalyptus?
<nitpick>Pandas eat bamboo; koalas eat eucalyptus.</nitpick>
#7
Old 12-11-2006, 10:34 AM
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Quote:
Originally Posted by Quiddity Glomfuster
According to some twin studies, they seem to also contain family names, mannerisms, and habits. Seems twins brought up in different homes end up marrying women with the same names or drinking their coffee exactly the same way or sharing many mannerisms that are peculiar to them. So if that can be inherited, then so can spiderweb-making.
I'm pretty sure those stories are false, or at least highly exaggerated.
#8
Old 12-11-2006, 11:07 AM
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Quote:
Originally Posted by Mangetout
I'm pretty sure those stories are false, or at least highly exaggerated.
I'm guessing it's closer to "If you compare enough bits of information, eventually you will find some matches." Kind of like reading Nostradamus. f you make enough vague predictions, eventually you can claim some of them are right.
#9
Old 12-11-2006, 11:17 AM
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Quote:
Originally Posted by chowder
The same way that birds know how to build nests, they just know
'They just know' isn't an answer.

The comparison with birds doesn't help. Small birds usually have (a) the nest they grew up in and (b) other visible bird nests and (c) the behaviour of other birds (including senior generations) to provide cues and clues. A spider can be born, live and die without seeing another spider, or another web, and yet build webs perfectly successfully.

Quote:
Originally Posted by mangetout
so why not, say, arranging neurons into the specific configuration necessary to provoke or enable a certain kind of behaviour or data processing
I guess the point here would be not whether or not genes could carry this kind of data, but whether or not they do. I have read about DNA and RNA and reverse transcriptase and so on, and from this I can see how the blueprint for an amino acid can be copied from parent to child. Personally, I haven't come across any explanation concerning how such a thing as the complicated sequence of steps required to build a spider's web could be passed on genetically, i.e. a process of coding and decoding, via known genetic mechanisms, that would enable this inheritance to work.

Quote:
Originally Posted by mangetout
Spiders' ability to build webs is information, but so is the arrangement of stripes on a zebra.
Apples and oranges. Stripes are physical structure. I know how information concerning the physical structure of the animal is stored and transmitted genetically. Building a web is a process that, at least from an anthropomorphic point of view (and this may be a classic error of thinking) seems to require knowledge or a 'blueprint'. It requires certain tasks to be performed before other tasks. The early stages make no sense without the later stages, and vice-versa. It also calls for tasks to be completed with respect to spatial orientation on a scale vastly greater than the animal itself. I don't know how this information or this ability can be coded and decoded genetically.
#10
Old 12-11-2006, 11:19 AM
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Quote:
Originally Posted by Tastes of Chocolate
I'm guessing it's closer to "If you compare enough bits of information, eventually you will find some matches." Kind of like reading Nostradamus. f you make enough vague predictions, eventually you can claim some of them are right.
Possibly, but the ones I'm thinking of (and Quiddity Glomfuster appears to be referring to) go along the lines of "twin boys adopted by different families were both named Bert (by their adoptive parents) and both grew up to be insurance salesmen; they both hated dogs, loved spicy food, both married women called bernadette, but both divorced after three years and remarried, both to women named Lucinda, who bore them two sons which both couples named Harry and Binky. They were unaware of each others' existence until the day when they were involved in a head-on collision (their cars were identical make, model, colour and year) - they had both been intending to drive to the other's home town!

AFAIK, these stories don't have any reality outside of the pages of Reader's Digest.
#11
Old 12-11-2006, 11:24 AM
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Quote:
Originally Posted by ianzin
Is the 'knowledge' inherited? I thought that only genes are inherited, and genes are codes for how to build the proteins that build the cells that build the creature. They don't contain 'blueprints' for webs.

So... how?
IANA spider guy but innate behaviors are pretty common.

http://cals.ncsu.edu/course/ent4...ior/index.html
#12
Old 12-11-2006, 11:26 AM
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Quote:
Originally Posted by Mangetout
I'm pretty sure those stories are false, or at least highly exaggerated.
Googling the subject produces a range of views, but there is a lot more than anecdotal evidence that identical twins raised separately share many traits. Here's a link
Quote:
The Minnesota Twin Study is a 20-year psychological and medical review of identical twins raised in different homes. The study has provided a huge body of critical information about the importance of genes and the environment in personality and behavior, as well as in the development of various illnesses.

Dr. Bouchard explains that the Minnesota research is actually a four-part study, looking at identical twins raised together and identical twins raised apart, and also at fraternal twins raised both apart and together. Comparisons to date indicate that the vast majority of measured individual traits, like personality and attitude, are due to a genetic effect. That was unexpected, he says; most researchers expected there would be more of a variance with some characteristics being strongly genetic and others strongly environmental.

He says he found it particularly surprising that religion showed up as having a stronger-than-average genetic link. He also discusses the heritability of mannerisms, job choice, happiness and choice of a mate. Genes appear to have little effect on choice of a mate, he says, probably because the pool of potential mates at the time of selection is too limited to allow for similar choices.
#13
Old 12-11-2006, 11:27 AM
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Quote:
Originally Posted by ianzin
Apples and oranges. Stripes are physical structure...
Not really; it's all encoded genetically. What we're talking about here is instinct - admittedly, quite organised, complex instinct in the case of spider webs, but once you concede that simple instinct (such as specific responses to a given stimulus) can be encoded and transmitted genetically, it should be no problem to conceive of more complex behaviours being able to being built in the same way.
#14
Old 12-11-2006, 11:42 AM
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Quote:
Originally Posted by ianzin
'They just know' isn't an answer.
Spider web-building behavior, like most other behavior of arthopods and most other invertebrates, is innate and hard-wired. Each species has their characteristic behaviors that results in the web typical of that species. Spiders do not learn this from their parents or any other spiders.

How exactly this happens is one of the great mysteries of biology. We do know that many behaviors are genetic; crosses between individuals from species or populations with different behaviors can result in offspring with intermediate behaviors. We don't at this point have a good idea of how this happens.

Quote:
The comparison with birds doesn't help. Small birds usually have (a) the nest they grew up in and (b) other visible bird nests and (c) the behaviour of other birds (including senior generations) to provide cues and clues.
Some bird behavior is learned, and some is innate. In general, nest-building behavior in birds is innate. A bird will build its species specific nest without ever having been taught to do so. In some birds, the song is innate; in others it must be learned from a parent.

Quote:
I guess the point here would be not whether or not genes could carry this kind of data, but whether or not they do. I have read about DNA and RNA and reverse transcriptase and so on, and from this I can see how the blueprint for an amino acid can be copied from parent to child. Personally, I haven't come across any explanation concerning how such a thing as the complicated sequence of steps required to build a spider's web could be passed on genetically, i.e. a process of coding and decoding, via known genetic mechanisms, that would enable this inheritance to work.
We know they do; we just don't know how. And you know almost as much about the mechanism as scientists do.
#15
Old 12-11-2006, 11:50 AM
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He says he found it particularly surprising that religion showed up as having a stronger-than-average genetic link
I would find this the least suprising aspect - I can easily see how certain individuals have brains pre-wired to accept the notion of a deity, much more than a preference for girls named Susan.

I'm still suspicious about these studies - there does seem to be a large element of confirmation bias involved.
#16
Old 12-11-2006, 11:58 AM
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Quote:
Originally Posted by ianzin
Building a web is a complicated business, involving an intricate series of inter-connected stages. How does a spider know what to do?
Well, they know not to use FrontPage ...
#17
Old 12-11-2006, 11:58 AM
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They Have read the FM.
#18
Old 12-11-2006, 01:12 PM
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Quote:
Originally Posted by Colibri
We don't at this point have a good idea of how this happens. // We know they do; we just don't know how.
Thank you, Colibri, for this very clear reply.

I agree with you that it seems a difficult question to answer. I also happen to think that web-building is a particularly taxing instance of what is referred to (both casually and in precise scientific contexts) as 'instinctive' behaviour. I think I'm fascinated by how much we know, or don't know, about the mechanisms which enable these 'instinctive' beahviours to be passed on genetically. I only completed high-school level biology, but I've met a few zoologists since and I have learned a little bit more here and there, and I still haven't come across a satisfying explanation (or maybe such an explanation would lie beyond my level of comprehension).
#19
Old 12-11-2006, 01:18 PM
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If you don't accept it as simple instinct, encoded and passed on as genes, I'm not sure what else there is to suggest instead. Magic?

True there might be something else beyond "genes", but outside of telepathic beams connecting the spider race, it's still got to come down to something passed on through a similar process as passing on genes. The only other suggestion I would have would be "trial and error", but I'm not sure spiders live long enough for that.
#20
Old 12-11-2006, 01:34 PM
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One conceptual problem you might be having is the idea of a "blueprint". It is highly unlikely that spiders have an innate blueprint for building a web, or birds have an innate blueprint for building a nest.

They don't have a blueprint, they have a "recipe". A set of stereotyped behaviors that, in the right environment, will result in a nest or web of a certain type being built. The spider doesn't have a concept of a finished web in its mind when it is building the web. Rather it has a certain set of instructions....perhaps something like:

1. Attach silk to a branch.
2. Jump off and wave around until you reach another branch.
3. Attach silk to branch, repeat until there is some signal that satiates the behavior.
4. At this point the spider has the "outline" of the web, an irregular polygon.
5. Then it climbs to the top and drops down to the bottom.
5. Then start weaving lines from the first crossline, each line a certain body length apart from each other. Stop when you get back to your first line.
6. At this point you've got the "spokes" of the web.
7. Then start adding the sticky webbing in a spiral from the center, stop when you reach the outer polygon.

Of course, how these "steps" are entered into the spider's firmware nervous system is unknown, but we can observe the methods animals use to construct structures. And they might use completely different rules for web building than I outlined above, but slight changes in the rules could result in very different finished webs, and very different starting evironments could do the same.

For another example, beaver dams. A beaver doesn't have a plan of a finished dam, it has a simple rule...when you hear running water, add more sticks and mud. Any time the dam starts to leak, the beaver hears the water trickle and gets the feeling it should pile more sticks on the dam. But if you play a tape recording of trickling water, the beavers will keep adding sticks until the dam is enourmously overbuilt. And of course, we still don't know on a physical or neurological level how or why the sound of trickling water makes a beaver want to cut down a tree and pile up the sticks, but it's a lot easier to imagine how this behavior could evolve from simpler behavior. Likely the ancestors of dam-building beavers built lodges out of sticks, and the sound of trickling water meant their home was leaking, and time to reinforce it. And a slight change in this behavior lead to the creation of dams.

So if you think "recipe", or a set of behavoirs that act together to create a structure, rather than "blueprint", animal construction behavior won't seem so baffling. Not that it's explained, exactly, but just that the behavior doesn't come out of nowhere.
#21
Old 12-11-2006, 02:48 PM
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Richard Dawkins, in his book River Out of Eden, talks about how complex instinctive behaviors can arise in relatively simple organisms. In the book, he posits how several complex insect behaviors might have arisen, particularly convincingly, IMHO, with respect to honeybee figure-eight "wiggle dances."

He also gives examples of how these complex behaviors can be short-circuited in unexpected circumstances. For example, when a bee dies, it emits a small amount of oleic acid. If a live honeybee is painted with a drop of oleic acid, it will be pushed out of the hive by the other bees, despite its protests and despite the bee being very much alive.

Also from the wiki entry, "a turkey will kill anything which moves unless it cries like a baby turkey. If the turkey is deaf, it will mercilessly kill its own babies."
#22
Old 12-11-2006, 03:01 PM
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Quote:
Originally Posted by robby
In the book, he posits how several complex insect behaviors might have arisen, particularly convincingly, IMHO, with respect to honeybee figure-eight "wiggle dances."
I read recently that honeybee dances do not encode directions to the source of the nectar, contrary to long-held beliefs. I'll look for it, but if anyone else read it and could provide a link I'd appreciate it.

Quote:
If a live honeybee is painted with a drop of oleic acid, it will be pushed out of the hive by the other bees, despite its protests and despite the bee being very much alive.
I'm predicting a Monty Python quote pretty soon in this thread.
#23
Old 12-11-2006, 04:45 PM
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Quote:
Originally Posted by Lemur866
One conceptual problem you might be having is the idea of a "blueprint". It is highly unlikely that spiders have an innate blueprint for building a web, or birds have an innate blueprint for building a nest.

They don't have a blueprint, they have a "recipe". A set of stereotyped behaviors that, in the right environment, will result in a nest or web of a certain type being built. The spider doesn't have a concept of a finished web in its mind when it is building the web. Rather it has a certain set of instructions....perhaps something like:

1. Attach silk to a branch.
2. Jump off and wave around until you reach another branch.
3. Attach silk to branch, repeat until there is some signal that satiates the behavior.
4. At this point the spider has the "outline" of the web, an irregular polygon.
5. Then it climbs to the top and drops down to the bottom.
5. Then start weaving lines from the first crossline, each line a certain body length apart from each other. Stop when you get back to your first line.
6. At this point you've got the "spokes" of the web.
7. Then start adding the sticky webbing in a spiral from the center, stop when you reach the outer polygon.

Of course, how these "steps" are entered into the spider's firmware nervous system is unknown, but we can observe the methods animals use to construct structures. And they might use completely different rules for web building than I outlined above, but slight changes in the rules could result in very different finished webs, and very different starting evironments could do the same.

For another example, beaver dams. A beaver doesn't have a plan of a finished dam, it has a simple rule...when you hear running water, add more sticks and mud. Any time the dam starts to leak, the beaver hears the water trickle and gets the feeling it should pile more sticks on the dam. But if you play a tape recording of trickling water, the beavers will keep adding sticks until the dam is enourmously overbuilt. And of course, we still don't know on a physical or neurological level how or why the sound of trickling water makes a beaver want to cut down a tree and pile up the sticks, but it's a lot easier to imagine how this behavior could evolve from simpler behavior. Likely the ancestors of dam-building beavers built lodges out of sticks, and the sound of trickling water meant their home was leaking, and time to reinforce it. And a slight change in this behavior lead to the creation of dams.

So if you think "recipe", or a set of behavoirs that act together to create a structure, rather than "blueprint", animal construction behavior won't seem so baffling. Not that it's explained, exactly, but just that the behavior doesn't come out of nowhere.
\

This is a good point. I assume nature found a relatively optimized way to transmit the information. Possibly the spider just has a few simple rules (not intended to even be a good guess, just an example):
1) Hang web in a circle like motion.
2) The distance between threads should be about x.
3) Stop after y circles.

The thing that amazes me is the amount of information that would need to be coded into DNA (body and brain structures, instincts, etc.). Are there enough pairs to code everything that is coded? Are there other chemicals involved that carry information that we are not giving credit? Is the information not really at a gene level? Maybe one pair is logically part of multiple information carrying structures simultaneously?
#24
Old 12-11-2006, 05:39 PM
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Quote:
Originally Posted by Sage Rat
If you don't accept it as simple instinct, encoded and passed on as genes, I'm not sure what else there is to suggest instead. Magic? // it's still got to come down to something passed on through a similar process as passing on genes.
Well, first of all, this isn't about what I am and am not willing to accept, which is neither here nor there. (Personally, I'm ready and willing to accept anything if there's good evidence to suggest it's the right thing to accept.)

What this is about is the factual answer to what I think is a fascinating question, and how much we know about it. I am quite willing to believe that the behaviour is somehow conveyed genetically. My problem is that I have never yet come across an explanation as to how this particular type of information is, or can be, conveyed, given what we know about genetics. I'm not saying such an explanation doesn't exist -- just that I haven't come across it yet. Nor has anyone else I've yet discussed this matter with.

I'm not a fundie, I don't have a problem with evolutionary theory, and I'm not trying to make a case for an explanation involving either magic, myth or faith. It's just that as far as I know we have at best an extremely limited understanding of how behaviours such as web-building are inherited, and I thought I'd see if the Teeming Millions could provide some illumination.

I happened to choose spiders and webs because I like spiders and I'm fascinated by them, and I think web-building is a particularly interesting and challenging example, more so than birds building nests or beavers making dams.
#25
Old 12-11-2006, 06:10 PM
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Quote:
Originally Posted by CurtC
I read recently that honeybee dances do not encode directions to the source of the nectar, contrary to long-held beliefs. I'll look for it, but if anyone else read it and could provide a link I'd appreciate it.
I'd be interested to see this, because I thought it had been demonstrated quite conclusively that the waggle dance did convey information regarding the direction (relative to the sun) of food sources - the experiments I saw involved a computer controlled robotic bee, programmed to dance in a specific way and resulting in statistically significant numbers of bees flying off in the expected direction afterwards.
#26
Old 12-12-2006, 01:56 AM
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How do you know how to breathe? Behavior can be "just there" in the genetic design of an organism. (I don't see why voluntary vs involuntary muscle movements would matter.)
#27
Old 12-12-2006, 03:40 AM
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Quote:
Originally Posted by Lemur866
For another example, beaver dams. A beaver doesn't have a plan of a finished dam, it has a simple rule...when you hear running water, add more sticks and mud. Any time the dam starts to leak, the beaver hears the water trickle and gets the feeling it should pile more sticks on the dam. But if you play a tape recording of trickling water, the beavers will keep adding sticks until the dam is enourmously overbuilt.
Is this true, or just an example made up to convey a point? Could you point me towards a cite because this seems like a pretty cool example.

To the OP, apologies that this board is being rather prickly, but you're certainly right to have stumbled upon a very complex question in neurobiology.

Here's one example that I think might help you to get a better grasp on this from the level you seem to be coming from: how do cells know what they should "grow up" to be?

That generic, globular "cell" that all of the 4th grade text books have doesn't really exist. Rather, every cell turns from a type of stem cell into a more specialized cell like a muscle fiber or a neuron. The way that this occurs is incredibly complex and basically cells have ways of "listening" to their surroundings to figure out how many of other type of cells there are out there and develop into the appropriate cell lineage. Again, very complex and we're just beginning to scratch the surface, but here's an example of a stem cell (a cell from a small embryo before those cells begin to develop into special tissues, etc.) that scientists have been able to grow into healthy pancratic cells (it's when these cells go bad that diabetes develops).
http://nature.com/nbt/journal/v2...s/nbt1259.html

Basically, they bathe the cells in a specific line of chemicals and they get that result. Certainly, a similar process takes place in your brain and it develops its own complex anatomy.

So, to address your issue directly, why couldn't that physical programming apply to neural connections as well to program innate behavior?
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#28
Old 12-12-2006, 08:03 AM
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This is a fascinating thread. Thank you, Ianzin.

Thank you Colibri for your great explanation, and reason for lack of available explanation. It is awesome what we still need to understand. I have had the good fortune to observe spiders weaving webs closely. This discussion is revolving around the most advanced web - the total orb web of the garden orb weavers and others who do a full orb. It is by far the most logical to use, but that leads me to ask if Lemur866 is observing a different starting behaviour.

Quote:
Originally Posted by Lemur866

2. Jump off and wave around until you reach another branch.
Those I have observed release silk into the breeze (which needs only be a very slight to catch it), until it makes contact with something on the other side. Then they race across and adjust that thread to make the initial strong cross thread. Do you know of species which jump off and wave around as described above?

I'm not being picky - I do realise you were giving an algorithm for example, rather than a scientifically pedantic response. I was wondering if there were species which did this.

Our garden orb weavers, in Australia, usually leave that thread when they take down the web in the morning and reuse it the following night if possible. If it is a totally still night, and they don;t have a trhead already there, I have watched spiders give up on getting that thread out, and not build a web for that night.

I have also watched successive generations of our black house spider - which started with a single female inside the shed where I work, and so I know almost certainly that the first young was the offspring of the mother I had been 'talking to' for two years. She never did respond, but I yakked away anyway. The mother died after the birth of her young.

The mother and child constructed their webs in the same place - these are cribellate webs - woolly not sticky - which get new parts each night constantly growing. They built in the corner of the window, which got very hot in the middle of summer, and both then went and made a new web behind a rug hanging from the window sill.

The intriguing thing was that the mother was very confident- she would stay out at night on the edge of her funnel in the web when I went over for a chat. Her child, even after over a year in residence, would not stay out. If I approached, she retreated. A third black house spider who took up residence would not even stay out when I turned the light on. Three spiders, same species, probably a mother and two offspring, and three consistently different behaviours.

I believe this is evidence of personality, and there is no reason to think spiders wouldn't have individual personalities just as other animals do.

So we are back to how much of personality is a response to environment and how much is genetically coded - as was raised in the twin studies.

Spiders are incredible!

Lynne
#29
Old 12-12-2006, 10:44 AM
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This may be my only chance to say 'Hi Opal!' without getting flamed for it, so I'm going to use it. Hi Opal! and thanks for playing. I may be completely wrong about this, and merely blinded by my own ignorance, but it seems to me that there's a difference between the example you provide ('knowing how to breathe') and similar, and the building of a spider's web.

Part of this difference lies in the fact that building a web is a construction project that has to be completed over a period of time, and a very complex one.

Building a web is a construction project on a scale far greater than the size of the spider. It involves (AFAIK) at least four distinct construction stages (initial lines; spokes; radial lines; finishing off, tautening, checking and optional addition of stickiness layer). These stages have to be completed in order. None serves any purpose except as part of a successfully completed web (ie all would otherwise be a huge waste of the spider's energy and resources).

Whatever the underlying instincts or neuro-biological rules that the spider is using / obeying, the 'algorithm' (using the word in a loose and colloquial way) has to be sophisticated enough to cope with whatever circumstances the web-building spider happens to find itself in. Even for one given web-spinning species in one region of the world, the spider might have to cope with a huge range of prevailing weather conditions, winds, available sites and possible anchor points. Building a web on rigid anchor points in an airless site (eg my old bicycle frame in a closed garage) is quite a distinct task from building one between a tree and a gorse bush while both are swaying in the night-time breeze.

Note also that each part of the web's construction has to have the 'correct' spatial relationship to other parts for the web to be successful, even though (as noted previously) the construction is on a scale sometimes scores of times greater than the size of the animal itself. And remember that the animal has (in most cases) virtually no vision beyond 'moving gray shapes immediately ahead', and certainly no way of 'visualising' what the web looks like to us, with our privileged 'overhead view'.

I think this degree of specialisation and complexity marks web-building as worthy of special consideration. I think it is a far more complex behaviour than either nest-building or dam-building, which seem to me to call for less complex 'algorithms' (again, using the word colloquially). I think that web-building presents or offers a special challenge if we want to account for it successfully in terms of hard-wired instinctive ability that is communicated genetically. I'm happy for this to be the explanation. I just think we've a long way to go before we can say we really understand it.
#30
Old 12-12-2006, 10:52 AM
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I don't see that there is any clear line where simple behaviour ends and complex behaviour begins; all living things have behaviours/actions built into them - some of these are conspicuously a mechanical function of construction, others are meta-actions built up from the interaction of many different sub-actions. Complexity is what makes it difficult to study and therefore a bit of a mystery at present - in much the same way that I can easily comprehend the way a transistor works, but find it difficult to fully comprehend and appreciate the totality of action performed by many tens of thousands of transistors acting together in the CPU of the computer from which I am posting this.
#31
Old 12-12-2006, 11:17 AM
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These stages have to be completed in order. None serves any purpose except as part of a successfully completed web (ie all would otherwise be a huge waste of the spider's energy and resources).
On the off chance you're invoking a sort of irreducible complexity argument, here, I'll point out that you can make a functional web by following the simple algorithm of "string strands of silk up every which way", and presumably the first web-spinners followed just such an algorithm. As the spiders evolved, so did their web-building behaviour, and the webs became more efficient in the process.
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#32
Old 12-12-2006, 12:20 PM
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Here's a couple of websites that repeat the story I told about beavers responding to sound, although I haven't found any research papers online to substantiate it.

http://naturealmanac.com/archive...aver_dams.html
http://wlapgov.bc.ca/vir/pa/Beaver-Guide.pdf

As for the steps taken by spiders to construct webs, those were purely made up.

Now, back to Ianzin's further questions. It isn't true that "partial" webs are useless. You're surely familiar with the webs known as "cobwebs", right? These are webs built by spider species that are constructed more or less at random. The spiders just run sticky threads every which way and build up a mass of threads. These simple web types are probably the ancestral web type, and the more elaborate orb webs evolved from simpler webs.

And you're correct that the spider can't see the completed web, which is why the notion of a blueprint is misleading. The spider isn't following a plan, it's performing behaviors that, if conditions are right, will result in the finished web.

One interesting thing about animal behavior, especially non-mammal behavior, is how easy it is to "break" the behavior. Put an egg under a bird and the bird will treat the egg as it's own egg and care for whatever hatches out of the egg. Even though cuckoos exploit this behavioral rigidity. I've put duck eggs under hens, and the hens take care of the baby ducks like their own chicks, although they get very upset when the ducklings go swimming. Or you have a situation where baby birds peck at a spot on their parents beak to stimulate regurgitation of food. But the baby birds will peck at a larger spot in preference to the parental spot.

So animal behaviors often only work in the environment they are adapted to. If the animal finds itself in an unexpected environment, the behaviors won't work. So an attempt to build a web in an unsuitable environment just doesn't work. So my suspicion is that these web building algorithms don't have as much flexibility as you might think...it's just that you don't see many failed attempts because those spiders don't live very long.
#33
Old 12-12-2006, 02:53 PM
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Quote:
Originally Posted by Lemur866
As for the steps taken by spiders to construct webs, those were purely made up.
Can you please clarify what you mean by this? If you are referring to the stages that I described earlier, I'm at a loss to understand what you mean by saying they were 'made up'.
#34
Old 12-12-2006, 03:19 PM
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When I described a stepwise algorithm for building a web, I just imagined one that could possibly work. Lynne pointed out that spiders actually use a different method to construct their outer guy lines.

But there really are plenty of spiders who don't create the classic orb webs, there are lots that make simpler webs that don't have that complex structure. So the complex webs didn't have to evolve at one step, they started from simple webs that became more complex via small steps.
#35
Old 12-12-2006, 03:34 PM
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I realize there is a vast difference in sophistication between breathing and building a web. My point was merely that our genetic material already has built into it directions for "activities" rather than physical structures. Thus, it doesn't seem difficult for me to take that a step further and say that some species' genetic information includes behaviors as complex as web building.
#36
Old 12-12-2006, 03:41 PM
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Quote:
Originally Posted by Colibri
Spider web-building behavior, like most other behavior of arthopods and most other invertebrates, is innate and hard-wired. Each species has their characteristic behaviors that results in the web typical of that species. Spiders do not learn this from their parents or any other spiders.

How exactly this happens is one of the great mysteries of biology. We do know that many behaviors are genetic; crosses between individuals from species or populations with different behaviors can result in offspring with intermediate behaviors. We don't at this point have a good idea of how this happens.
To further clarify (or obscure, depending on your point of view) Darwinian natural selection posits that innate characteristics which promote reproductive fitness are inhereted, but acquired characteristics (which are learned or developed by a creature during its lifetime) are not. Lamarck proposed the opposite; that a blacksmith's child would have big forearms because his father developed them performing his trade. Knowing, as we do now, of Mendelian genetics, we realize that this is a fundamental absurdity, but in the mid- to late-19th Century, this was not at all clear.

The ability to build a web is a benefit to the spider, hence it evolved progressively complex abilities to build and maintain webs. Since we have a very limited fossil history of the development of spiders we can't really say precisely how this ability came about and the timeline for development, but there are clearly different levels of capability and complexity between different species of spiders, from those which can't spin webs at all to those that make the elaborate spiralling webs across your front porch.

Web building, by the way, is really not that complex of an activity. You can easily write a program in, say, LOGO or Lisp (or if you want to endure real pain, C++ or Java) that will make a web-shaped result. You can program it to make the lateral members red (sticky) and the radial members blue (not sticky) just like a real web. It's not hard to imagine that a neural complex sophisticated enough to handle respiration and do even basic visual and auditory recognition could have web-making algorithms to make a web.

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#37
Old 12-12-2006, 04:17 PM
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I remembered years ago reading about the effects of different drugs on spider's innate web building abilities. Here's a site that deals with it (wikipedia has a section too):

http://trinity.edu/jdunn/spiderdrugs.htm

Not entirely convinced the webs are that different. The LSD one just seems a little edited to make it look mildly trippy.
#38
Old 12-12-2006, 05:36 PM
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Quote:
Originally Posted by lynne-42
Those I have observed release silk into the breeze (which needs only be a very slight to catch it), until it makes contact with something on the other side. Then they race across and adjust that thread to make the initial strong cross thread.

...

Spiders are incredible!

Lynne
In fact, here is a link that has (at the bottom) a nice diagram of the construction steps involved in one type of orb web: here.

I thought that I remembered reading somewhere that the 3D funnel webs were more complicated to construct than an orb web - but now I can't quickly find a reference. (I'll look more later.)

Fascinating question - but I'll bet you could ask it in a similar vein: when an object approaches our eyeball (external stimulus as input) why do we blink and/or flinch involuntarily (behavior as response)? We don't know how it is genetically transmitted, but that is a behavior that is hardwired in us. Another, now that I think about it, is shutting our eyes during a sneeze. So behavior can be carried in our genetic code - to build complicated patterns of behavior, link a series of simpler behaviors together (as Lemur866 and Colibri suggested).
#39
Old 12-12-2006, 06:20 PM
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Originally Posted by Stranger On A Train
Web building, by the way, is really not that complex of an activity. You can easily write a program in, say, LOGO or Lisp (or if you want to endure real pain, C++ or Java) that will make a web-shaped result.
A quick Google turns up, for example: Analysing Spider Web-building Behaviour with Rule-based Simulations and Genetic Algorithms and then a Q&A with one of the authors.
#40
Old 12-12-2006, 07:28 PM
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Quote:
Originally Posted by Stranger On A Train
Web building, by the way, is really not that complex of an activity. You can easily write a program in, say, LOGO or Lisp (or if you want to endure real pain, C++ or Java) that will make a web-shaped result.
Yes, it is easy to write a program that will produce a web-shaped result. Many people can do it. But it is not easy to write a program that will run inside a machine that will produce an actual web structure in the real world, with next to no visual pattern recognition, given arbitrary starting conditions and possibly difficult weather conditions. This is very different, and no-one has been able to do it.

I don't think it was your intention, SOAT, to trivialise the 'program' needed inside the spider's head. But I do think that this and other responses along the lines of 'hey, it's really not all that complicated' run the danger of seriously under-estimating the complexity of the task and the corresponding complexity of the 'program' that has had to evolve. It is not just a case of 'go round and round and lay equi-distant threads until you find it's the middle'. The evolved 'program' has to accommodate a huge range of possible problems, hindrances, prevailing conditions, situations, locations and events that can occur during web-building.
Quote:
Originally Posted by Stranger On A Train
It's not hard to imagine that a neural complex sophisticated enough to handle respiration and do even basic visual and auditory recognition could have web-making algorithms to make a web.
Point taken and I agree. That having been said, I'm not aware of any spider with auditory recognition, even at a 'basic' level. And the visual apparatus of most of the spiders I'm referring to (AFAIK) is very poor. Vision only plays a role during the very final stages of predation, and allows the spider to see that there is an insect-sized shape in the middle of visual field, and that it moves.
#41
Old 12-12-2006, 08:12 PM
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Originally Posted by ianzin
I don't think it was your intention, SOAT, to trivialise the 'program' needed inside the spider's head. But I do think that this and other responses along the lines of 'hey, it's really not all that complicated' run the danger of seriously under-estimating the complexity of the task and the corresponding complexity of the 'program' that has had to evolve. It is not just a case of 'go round and round and lay equi-distant threads until you find it's the middle'. The evolved 'program' has to accommodate a huge range of possible problems, hindrances, prevailing conditions, situations, locations and events that can occur during web-building.
You're right, I don't mean to trivalize the incredible capability of a machine as complex and intricate as even something as biologically simple as a spider. But once you have said organism, the instructions to build a weapon are, relatively speaking, pretty simple, requiring nothing that we would call awareness or cognition beyond a simple instruction set. The spider building a web is a particularly good example of this; while you note that it must "accomodate a huge range of possible problems, hindrances, prevailing conditions, situations, locations and events," but truthfully it doesn't accomdate these things except by incidental design.

A spider doesn't understand that building a web in a doorway is a waste of valuable time and energy, nor will it learn when the web is destroyed not to build there again if it's an otherwise ideal spot. The instructions for building a web are really quite simple, and the spider can be tricked into doing it wrong by altering conditions and cues in ways that the programming doesn't allow for. In other words, spiders don't exhibit awareness or judgement based upon experience; they build where, when, and how because that's what the hardwired instructions tell them to do. Most spiders fail to reproduce and die (hence, why they are hatched by the hundreds); those who survive to reproduct statistically increase the fitness of the species by passing on the traits that permitted them an advantage.

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#42
Old 12-13-2006, 02:44 AM
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Spiders in general are interesting lessons in evolutionary specialization—particularly the web-builders. Those that I find most incredible are the ones that use their silk actively, as a weapon, to hunt for prey (i.e. Bola Spider, Net Throwing spider). I imagine their natural selection journey was even more complicated than the static web builders. (Also, of interest: The record holder for the highest-flying animal is the ballooning spider).

http://szgdocent.org/resource/ff/f-ssilk.htm

http://geocities.com/brisbane_we...NetCasting.htm

http://geocities.com/brisbane_we...ntificPage.htm

http://homepage2.nifty.com/singingsa..._gossamer.html
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#43
Old 12-14-2006, 07:41 AM
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Quote:
Originally Posted by Stranger On A Train
You're right, I don't mean to trivalize the incredible capability of a machine as complex and intricate as even something as biologically simple as a spider. ...

In other words, spiders don't exhibit awareness or judgement based upon experience; ...

Stranger
I am not sure what makes you claim spiders are biologically simple.

I also find the claim that they don't learn by experience remarkable. All you need to do is a web search on the jumping spider, Portia, such as here .
Incredible - and smart and anything but simple.

Lynne
#44
Old 12-14-2006, 07:49 AM
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Originally Posted by Schuyler
In fact, here is a link that has (at the bottom) a nice diagram of the construction steps involved in one type of orb web: here.

I thought that I remembered reading somewhere that the 3D funnel webs were more complicated to construct than an orb web - but now I can't quickly find a reference. (I'll look more later.)
I should declare a vested interest here and say that I am not only obsessed by spiders, but also writing a book on them, so all your answers are sending me in all sorts of directions. But I think it is ethical I tell you that.

That site was great, Schuyler, and I would be really pleased if you could remember the reference to funnel webs. What we call funnel-web spiders in Australia are 'primitive' spiders who live in burrows. They have silk trap lines coming out from their silk lined burrows, which led to the term 'funnel'. This includes the Sydney funnel-web which is deadly.

Other countries call 'modern' spiders which build webs with funnels in them 'funnel-webs', for pretty logical reasons. We have them, too. I suspect it is the webs of the latter you mean and I am very keen to know if you can come up with a reference.

Lynne
#45
Old 12-14-2006, 08:53 AM
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Not completely related to the subject, but just an interesting website.Kythereia

http://spiderwebfarm.com/

This "Spider Web Farm" is just a little farm in a no-name town in Vermont. Basically during the Spring and Summer they lure the spiders into empty frames and get them to spin webs. Then they'll go through several light spray painting and aerosolyzed gluing until they can pull a piece of wood through the frame and capture the web. I met this wonderful couple and they have a map of the world in their workshop that shows visitors from all over the world. And I have one of my own hanging up in my room.

This is why Vermont is my favorite state, it is covered, like little nooks and crannies, with all sort of little hidden gems like this.
#46
Old 12-14-2006, 03:12 PM
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Originally Posted by Stranger On A Train
once you have said organism, the instructions to build a weapon are, relatively speaking, pretty simple // The instructions for building a web are really quite simple
I'd just like to add that I profoundly disagree (in a friendly way - this isn't GD or the Pit), and I think your qualifiers ('relatively speaking' and 'pretty') are only there to hedge your bets.

I have no idea what the neurological 'program' (using the term loosely) for web-building behaviour looks like. But I would suggest it's more complex, by many orders of magnitude, than any instruction set or computer program that we humans know how to write. I know plenty of men and women who can write the software for, say, a busy trading floor or a jumbo jet's navigational system. I don't know anyone who can write a program that you can run -- inside any machine you care to imagine or construct -- such that if you drop the machine at random on a bush, it will be able to work out how to build a web somewhere in that vicinity. And remember, this program has to work without any visual input beyond the extreme near field.

I know that the 'program' can be derailed (ie you can trick spiders into building webs that don't make sense). But this only indicates that the program has limitations, not that it isn't complex. Any piece of software can be derailed, no matter how complex, if you provide input that it wasn't designed to handle. And whereas every piece of human software ever written is prone to 'crashing', such that the system locks and needs to be rebooted, I've never seen a spider simply 'crash' or lock into a static position such that it seems to need 're-booting'. Somehow, the program never actually seizes up. Even if you do your best to derail it.

Simple? I don't think so. Not even 'relatively' so. Just my opinion.
#47
Old 12-14-2006, 04:09 PM
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Originally Posted by lynne-42
I am not sure what makes you claim spiders are biologically simple.

I also find the claim that they don't learn by experience remarkable. All you need to do is a web search on the jumping spider, Portia, such as here .
Incredible - and smart and anything but simple.
First of all, I was speaking of the anatomical and neurological simplicity of spiders relative to other animals of orders Sauropsida (reptiles), Aves (birds), or Mammalia (mammals). Certainly spiders are complex than a single-celled organism, and vastly more complex and compact than any mechanism we could build to perform the same tasks, but they are a stone hammer to a rocket booster in comparison to a dog or parrot.

Second, the context was speaking in terms of web-building spiders; generally speaking, it is accepted that a hunting predator will be more sophisticated and aware than one which traps prey. It is inarguable that jumping spiders (family Salticidae) are the most complex and intelligent of all spiders; in comparison to even the most primitive rodent, however, it's unclear (despite the linked pop science article which is short on detail and long on misapprehensions, such as spiders being like "other insects") that it can be considered on par in terms of cognitive problem solving capability.

Third, while there's no question that the biological machinery and neural sophistication of even a simple organism like a spider is vastly more reliable than a computer (which is understandable; Intel and AMD are going on a third decade of building microprocessors, whereas Nature has had a couple of billion years to refine brains), the complexity of a set of algorithms to replicate the behavior of web-building spiders is not that great, certainly not compared to a mouse or a moose.

Even assuming the kind of complex visual processing capability that the linked article posits for the jumping spider doesn't translate directly into cognitive capability; many creatures have much more capable and and accute eyesight than primates, or even other complex and intelligent animals like the bear or octopus. "Knowing" (as contrasted with conditioned response to external stimuli) requires a degree of awareness both of the environment and one's place in it, and a complex response to new stimuli (curiosity, caution, probing, trial and error, progressive learning). A jumping spider might exhibit these behaviors to a limited extent, but doubtless not to the same degree as a neurologically more complex creature which undergoes a long period of rearing and exploratory experience. And certainy web-building spiders display almost no degree of cognition or broad-scale comprehension beyond very simple operant conditioning.

Spiders know how to build webs not by trial and error (the way we learn how to do things) but because the conditions and cues that lead to the activities of web-building are coded genetically into what passes for their brains.

Stranger
#48
Old 12-14-2006, 04:10 PM
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I've seen a spider lock up into a static position from a re-booting. Actually it may have been the first booting that did it. Poor little spider
#49
Old 12-14-2006, 07:33 PM
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Quote:
Originally Posted by Quiddity Glomfuster
According to some twin studies, they seem to also contain family names, mannerisms, and habits. Seems twins brought up in different homes end up marrying women with the same names or drinking their coffee exactly the same way or sharing many mannerisms that are peculiar to them. So if that can be inherited, then so can spiderweb-making.

If you think of it, how does any creature know anything? Why will pandas only eat eucalyptus? There's a whole dang forest out there; nothing's stopping them from munching down on any other leaf or tree or even chomping a snake but they don't.
Actually, the twin studies don't mean that those are inherited, just that they are shared. To show they were inherited, you'd have to show that parents/children married people with the same names, etc.

w.
#50
Old 12-14-2006, 10:38 PM
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Quote:
Originally Posted by Stranger On A Train
First of all, I was speaking of the anatomical and neurological simplicity of spiders relative to other animals of orders Sauropsida (reptiles), Aves (birds), or Mammalia (mammals). Certainly spiders are complex than a single-celled organism, and vastly more complex and compact than any mechanism we could build to perform the same tasks, but they are a stone hammer to a rocket booster in comparison to a dog or parrot.
I still can't agree. I have just spent two years writing a book on crocodilians (order Crocodylia) that is crocodiles, alligators, caimans and the gharial. I am now engrossed in my favourite animals - spiders - for my next book. I am not finding the physiology any simpler. The gospel on spider biology is Rainer F. Foelix's Biology of Spiders, and for complexity in anatomy, these guys lack nothing! The web builders depend on very sensitive response to the vibrations of anything in the web to assess not only the location in the web, but the size and nature of the animal trapped, and then behave accordingly. If you start saying all this can be programmed, it can be argued that everything we do can be as well.

I have the same word length on the spider book as I did on crocodilians, and will struggle terribly with it - there is just so much more variety in spiders. That's not to knock down the crocs - their heart and immune systems, among many other aspects, are extraordinary and more advanced than ours in some ways. But like us, they have nothing remotely like the spider families ability to create a huge range of silk types - a single species can create a variety of silks for different purposes. So comparing animal species for any single ability is worrying - you need to consider them in terms of the ecological niches for which they have evolved.

Quote:
Second, the context was speaking in terms of web-building spiders; generally speaking, it is accepted that a hunting predator will be more sophisticated and aware than one which traps prey.
I struggle with this claim as well. Let me give a single example of an orb weaver. I have the article in front of me if you want the reference. Fifty Australian leaf curling spiders (Phonognatha graeffei) were taken into a lab - so out of their environment and where the 'program' was supposed to work. 33 managed to build a web, 17 didn't. Programming? All were in an identical situation. They were placed in a frame and given a choice of leaves. 24 of the 33, chose green leaves which are much more suitable for creating their leaf retreats in the middle of their orbs. The other 9 chose dry leaves. The article then says: "Although the spiders usually selected a leaf for their retreat before completing construction of the web, the decision process appears to be ongoing: four spiders that initially selected dry, brown leaves subsequently removed them from the web in favour of moist, green leaves."

This is in the lab with leaves placed on the base of the frame - nothing like their usual environment.

Quote:
"Knowing" (as contrasted with conditioned response to external stimuli) requires a degree of awareness both of the environment and one's place in it, and a complex response to new stimuli (curiosity, caution, probing, trial and error, progressive learning).
So how did these incredibly simple animals with no "knowing", in your opinion, manage to build its web in totally unnatural environment, and then display a decision making process adapting to the situation in hand - including the trial and error you dismiss as being possible for spiders?

I am not arguing that these are the most intellectually capable creatures, but simple they are not. They are far from studied to the degree other animals are. In fact, it is estimated thet the 40,000 or so known species may be less than half of those on earth. We haven't even classified them all yet, let alone studied their cognitive abilities. In fact, the experts I talked to when investigating crocodilians all acknowledged they were far from intelligent - in the way we humans define intelligence. Armchair experts on crocs tend to claim they are intelligent, those who work with them don't. They don't really need great cognitive abilities in the ecological niche they have so successfully evolved to fill.

Quote:
Most spiders fail to reproduce and die (hence, why they are hatched by the hundreds); those who survive to reproduct statistically increase the fitness of the species by passing on the traits that permitted them an advantage.
As do many animal species, including the reptiles you quote as so vastly superior. Crocodiles don't need great intelligence in their lofty position at the top of the food chain - when they get there. 99% of saltwater crocodiles don't make it to their first birthday - and just like the spiders, they fail to reproduce and die. (Reference: my own book! Oh, and the the references quoted in it.)

I better get back to studying the physiology of spiders - it's complex stuff!

Lynne
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