All You Wanted to Know About Spider Webs, Except Their Evolution

Each issue of Current Biology contains a Primer on some interesting subject.  The May 24 issue had one about spider webs.¹  Fritz Vollrath shared some amazing details about this unique product of the lowly spider, but gave a strange explanation for how the capability to spin strong-as-steel nets evolved.  First, the factoids:

• Structure:  …the… common garden spider… has evolved to take out-of-plane loads at optimized deflections.  To be able to do so, this web needs to incorporate into one structure the mechanical properties of very different types of silk: the fairly stiff, radius silk threads and the extremely soft, extensible and sticky capture silk threads, which are fixed on the radii by stringy silk cement.  (Emphasis added in all quotes.)
• Heritage:  Most of the hundred or so spider families have web-building members.  Their webs range from two-dimensional sheets to three-dimensional tangles, with members of ten families building the familiar orb web.
• Signaling:  The spider’s web is primarily a trap, mostly for insects; it retains the contacting insect and informs the waiting spider about the location and status of the prey.  Whether it is a static filter or a dynamic net swaying in the wind, the web always relays vibratory signals of considerable complexity.
• Geometry:  The great ecological diversity of the potential prey is reflected in the great diversity of web designs.  Of these, the orbicular web has attracted special attention because of its ubiquity, pleasing geometry, obvious functionality and, not least, its apparent structural simplicity.
• Technique:  The typical spider web … is the spider’s inherited ‘signature’, which – although unlearned – is modified predictably by the environment.  The web is many times the spider’s size; accordingly, the decision rules guiding the animal’s locomotory and manipulative movements can best be described (and analysed) as orientation behaviour.  Vollrath says that model spider robots can generate digitized spider webs, and show that a “small number of very simple behaviour patterns are sufficient to generate accurately the characteristics of a real spiderweb.”
• Technology:  The common garden spider Araneus diadematus, like other orb weavers of the ecribellate families, employs in each bead of its capture threads a microscopic ‘windlass’ mechanism that allows supreme extendibility while absorbing the high kinetic energy of the prey without breaking. Another species “combs out its capture silk to form a loosely twisted, dry rope with a mechanical coil-and-spring that sticks to prey using electrostatic forces.”
• Materials science:  Spider silk is not a single-protein biopolymer.  In addition to the spidroins, its main protein constituents, the typical spider dragline silk contains many different organic and inorganic components, such as neurotransmitter peptides, glyco-proteins, lipids, sugars, phosphates, calcium, potassium and sulphur….
  Functionally, silks can be viewed as a ‘filled rubber’, in which crystallites provide the strength and a matrix provides the elasticity: in combination, these two components give the silk its toughness.
• Manufacture:  At present we do not know the precise mechanisms by which different silk proteins fold and assemble in the ‘spinning ducts’ of the various and diverse spider glands.  Some initial insights have been gained, however, into the silk pathway of one typical spider silk: the dragline silk produced by the major ampullate glands of the golden silk spider … Here, as in all other spider silks, the liquid crystalline silk feedstock is prepared by specialist cells in the gland wall and stored in the lumen.  As with most other silks, this precursor silk is then converted into the solid fibre by extrusion through the tubular taper of a duct, where the enormously long … silk molecules first unfold and are then cross-linked.
      In Nephila, the fibre-forming zone has the shape and function of a hyperbolic extrusion die.  Here a small drop in the pH combined with the elongational flow of the molecules effects the transformation from liquid to solid silk…. the elongational flow helps to define the molecular orientations throughout the duct, and that a combination of solvent (water) extrusion and subsequent acidification helps the process of alignment and folding.  The cuticle of the gland’s duct facilitates the rapid removal of water and provides the proton pump for the acid bath.  In this way the spider uses a liquid crystalline spinning process which, in terms of human engineering, is highly advanced.

In the middle of the primer, Vollrath tackled the specific question, “How are webs thought to have evolved?”

Spider web structures and silks began their co-evolution about 400 million years ago, at first probably as a protein cover to protect the animal’s eggs and young.  Webs then evolved different functions, including acting as a kind of wall-paper for the animal’s burrow and modifying the hole into a simple trap by radiating lines that inform the lurking spider about things beetling around outside.  Even such simple lines expand the animal’s anatomical phenotype many fold by incorporating the body into an extensive silken net.  The aerial webs of the ‘modern’ spiders began to evolve perhaps 200 million years ago and are superb examples of ‘extended anatomy’.  These webs also nicely illustrate the close interaction of material and behaviour which clearly are two separately encoded yet functionally inter-linked character traits.

This seems to say that they evolved because they evolved. 

¹Fritz Vollrath, “Spider’s webs,” Current Biology, Vol 15, R364-R365, 24 May 2005.

This is a prime example of the leaps of faith rampant among Darwinians, who can discuss with apparent wonder the technologies of the animal kingdom – capabilities that dwarf human efforts based on intelligent engineering – then say they just evolved, with utter, implicit, and complete faith in the inspired Word of Charlie, who alone does wonders.  Then they have the audacity to accuse non-Darwinians of relying on faith instead of science.
    Vollrath apparently was not at all aware of nor troubled by the fact that he dodged the question about evolution.  How did the spider web evolve?  It evolved, he said.  Any skill or technology needed was available to the spider with the snap of the evolutionary fingers.  Example: certain spiders “have evolved to produce web fibres that have an aqueous coating, supplied and maintained by hygroscopic compounds to attract the required water molecules from the atmosphere.”  How did the spider find these hygroscopic compounds and incorporate them into the production line?  It evolved.
    That explanation is all-sufficient.  The precise acidity control?  It evolved.  The hyperbolic extrusion die?  It evolved.  The exact recipe of proteins, sugars, phosphates, calcium, sulfur, neurotransmitter peptides and other organic and inorganic ingredients that yielded a substance humans cannot emulate?  It evolved.  The ability to control the solidification and folding at exactly the right time and place?  It evolved.  The ability to sort out tough silks and soft, flexible sticky silks into a radial pattern?  It evolved.  The skill to snare insects, detect their presence, and get to them without getting stuck itself?  It evolved.
    It evolved because it evolved: that is apparently enough intellectual content to satisfy a brainwashed Darwinist.  Some humans build webs, too; the tangled kind, spun by self-deception.  Watch from a safe distance.