These explanatory illustrations show structures and mechanical ideas. The field photographs within the article record real spiders; each has its own species label, observation notes, photographer credit, and reuse license.
A web is more than its thread. Fiber chemistry sets what a line can do; arrangement decides how force travels, where energy is stored, and whether prey stays caught. Architecture turns silk from a material into a machine: intercept, deform, dissipate, retain—or, in non-trap uses, stabilize a jump or mark a path.
This page expands WebTug’s architecture chapter. It pairs each of the six roster strategies with a force-path reading and keeps the boundary between living structures and arcade visuals explicit.
Why this matters
Students often treat “sticky silk” as the whole explanation. Many capture systems fail or succeed because of geometry, pretension, anchor compliance, and which threads take the first hit. Reading webs as machines connects biology to introductory mechanics without pretending a browser demo is a full finite-element model.
01 — Orb: radial frame + capture spiral
Araneus trifolium in an orb web outlined by fog droplets in San Francisco.
Look closely: Trace one spoke outward from the spider, then follow a curved spiral strand across several spokes. The large visible beads are fog water; do not mistake them for a magnified photograph of microscopic capture-glue droplets.
The photographer combined multiple focus planes (focus stacking).
Photo: Brocken Inaglory · CC BY-SA 3.0 · Original / license record. Resized and converted to WebP; original composition retained.
Orb webs: stopping an impact
Trace impact energy through an orb, distinguish stopping from sticking, and compare rebound in the lab.
Jump to a chapter
Original WebTug explanation with animated teaching diagrams and credited still photographs. On-screen text carries the lesson; there is no audio narration.
Diagrams simplify the science. Animation timing and diagram dimensions are illustrative, not measurements of live spiders.
Compare orb rebound →Read the full transcript
- Read the web's structure
This still photograph shows a shamrock orb-weaver's web. Look for spokes running outward and a capture spiral crossing between them.
- An insect brings the energy
A flying insect arrives with kinetic energy. On contact, the web deforms: several silk threads help carry the load.
- Stopping and sticking have different jobs
In the studied orb webs, radial threads absorbed most impact energy. The glue-coated spiral helps retain prey after contact.
- Stretch does more than store energy
Some energy returns as the web recoils. Some dissipates within stretching silk, reducing energy available to throw the insect back out.
- Simplify the whole web
Our lab replaces many threads with one spring and damper. Its settings illustrate behavior; they are not measurements of this photographed web.
- Which web rebounds more?
Keep impact energy and stiffness fixed. Change only energy loss, replay both settings, and compare the size of the rebound.
Scientific sources and media credits
Araneus trifolium — Araneus trifolium and its web with fog droplets.jpg by Brocken Inaglory, CC BY-SA 3.0. Photograph fitted within the video without changing its composition; labels and animated diagrams added around it. The photographer combined multiple focus planes (focus stacking).
Script, diagrams, animation, and editing: WebTug, September 27, 2026. This video adaptation is available under CC BY-SA 4.0; individual photographs retain their credited licenses.
Watch the original publisher’s film for more detail
Machine job: Intercept flying prey, deform, spread impact energy, and retain the insect long enough for the spider to arrive.
Force paths: Stiffer radial threads carry load away from the impact site. The more extensible capture spiral deforms locally and, with glue in a typical glue-spiral orb, helps prevent immediate escape. Impact energy can become fiber stretch and whole-web motion, then be dissipated through internal material losses and aerodynamic drag. Movement at the anchors also changes how the structure responds.
Teaching model on WebTug: After impact, a simplified damped oscillator stands in for a many-thread network (m·x″ + c·x′ + k·x = 0 in the Spider Physics Lab). Primary research pointer: Sensenig and colleagues on radial threads and energy absorption in orb webs.
Limitation: One effective spring and damper cannot encode humidity, glue droplets, exact impact location, or every silk type in the sheet.
02 — Slingshot triangle: preload, then release
Triangle webs: energy before impact
Follow a triangle weaver's loading and release sequence, then test how preload changes the lab's starting extension.
Jump to a chapter
Original WebTug explanation with animated teaching diagrams and credited still photographs. On-screen text carries the lesson; there is no audio narration.
Diagrams simplify the science. Animation timing and diagram dimensions are illustrative, not measurements of live spiders.
Compare triangle preload →Read the full transcript
- Meet the triangle weaver
Hyptiotes cavatus builds a triangular web. This still photograph introduces the spider; the following diagrams explain its moving trap.
- Load the silk before the strike
The spider repeatedly tightens a separate anchor line with its legs. Muscular work builds elastic energy in the stretched web.
- Release the held line
When prey contacts the web, the spider releases its grip. Stored energy accelerates both spider and web toward the insect.
- Motion brings more silk into contact
The spider's sudden halt makes the web jerk and wrap additional capture threads around prey. Loading, release, and stopping work together.
- A spring is a simplification
Our lab uses one damped spring. A living triangle web has multiple lines and staged releases; its preload is not calibrated here.
- What changes with more preload?
Keep stiffness and energy loss fixed. Increase preload energy, then compare the loaded extension and motion after release.
Scientific sources and media credits
Hyptiotes cavatus — Triangle-web Spider - Hyptiotes cavatus, Julie Metz Wetlands, Woodbridge, Virginia.jpg by Judy Gallagher, CC BY 2.0. Photograph fitted within the video without changing its composition; labels and animated diagrams added around it.
Script, diagrams, animation, and editing: WebTug, September 27, 2026. This video adaptation is available under CC BY-SA 4.0; individual photographs retain their credited licenses.
Watch the original publisher’s film for more detail
Machine job: Store elastic energy before prey arrives; release it so spider and web move toward the target.
Force paths: The spider pulls an anchor line, raising tension in the triangular sheet. When prey contacts the web, the spider releases its hold and stored energy drives rapid motion. Geometry is sparse compared with a full orb; the animal’s active pretension is part of the machine.
Teaching model: Ideal spring energy Eₛ = ½ k (Δx)² as a visible preload metaphor. Primary research pointer: Han and colleagues on Hyptiotes elastic amplification.
Limitation: Real triangle webs use multiple lines and can release in stages; the demo shows one spring-like preload for clarity.
03 — Casting net: portable mesh, active throw
Net casting: move the capture surface
Connect a handheld capture mesh with visual hunting, then isolate net stretch in a schematic comparison.
Jump to a chapter
Original WebTug explanation with animated teaching diagrams and credited still photographs. On-screen text carries the lesson; there is no audio narration.
Diagrams simplify the science. Animation timing and diagram dimensions are illustrative, not measurements of live spiders.
Compare net stretch →Read the full transcript
- A net held by six legs
This still photograph introduces Deinopis spinosa. It hunts with a small net held between its front three pairs of legs.
- Take the mesh to the prey
The spider stretches its woolly silk net and actively casts it over prey. Its legs position the capture surface during the strike.
- Seeing helps guide the strike
Researchers temporarily covered the enlarged eyes. The spiders then struggled to catch walking prey, showing how vision supports nocturnal hunting.
- Area changes with both dimensions
In our schematic, stretching increases mesh width and height. That enlarges its coverage, while cast reach sets how far it travels.
- Separate the model from the animal
This simplified cast isolates reach, stretch, and settling. It does not reproduce the spider's sensing, leg mechanics, or three-dimensional strike.
- Which net covers more space?
Keep reach and settling fixed; change net stretch, replay both settings, and compare mesh width during the cast.
Scientific sources and media credits
Deinopis spinosa — Deinopis spinosa foraging at night.jpg by Jstaf13, CC BY-SA 4.0. Photograph fitted within the video without changing its composition; labels and animated diagrams added around it.
Script, diagrams, animation, and editing: WebTug, September 27, 2026. This video adaptation is available under CC BY-SA 4.0; individual photographs retain their credited licenses.
Deinopis spinosa holds a small capture net while foraging at night.
Look closely: Find the pale mesh in front of the body. It is a small portable capture surface, unlike the fixed orb in the comparison photograph. The original image is shown without enlarging its detail.
Photo: Jstaf13 · CC BY-SA 4.0 · Original / license record. Resized and converted to WebP; original composition retained.
Watch Cornell’s recorded forward and backward strikes alongside the net-caster profile.
Machine job: Take the capture surface to the prey instead of waiting on a fixed flight path.
Force paths: The spider holds a small stretchable net with the front legs, expands it, and casts it over the target. Force and area depend on how the mesh is stretched and aimed. Sensing and timing matter as much as passive dissipation.
Teaching model: Stretch force approximating F ≈ k·Δx, with area proportional to the square of scale only when the net stretches similarly in both dimensions. Primary research pointer: Stafstrom and Hebets on net-caster vision and prey capture; the University of Florida Deinopis spinosa account supplies natural-history context. The linear force relation is WebTug’s teaching approximation, not a constitutive law established by that vision study.
Limitation: The diagram isolates net stretch and active reach; it does not reproduce leg hydraulics or full 3-D strike dynamics.
04 — Bolas: line + adhesive mass + lure
Bolas: lure, flick, and adhere
See how chemical attraction, active movement, and deformable glue combine, then test a passive pendulum analogy.
Jump to a chapter
Original WebTug explanation with animated teaching diagrams and credited still photographs. On-screen text carries the lesson; there is no audio narration.
Diagrams simplify the science. Animation timing and diagram dimensions are illustrative, not measurements of live spiders.
Compare bolas line length →Read the full transcript
- A capture device on one line
This still photograph introduces Mastophora hutchinsoni. Hunting females use a silk line ending in an adhesive droplet: the bolas.
- Bring the target within reach
The spider releases chemical signals resembling female moth pheromones. Male moths approach, bringing a flying target close to the sticky droplet.
- The spider supplies the flick
An active leg movement sends the bolas toward the moth. The line and droplet stretch as the capture device accelerates.
- The glue changes shape
During contact, the adhesive spreads into the moth's scales. The deformable droplet and silk help manage the struggling prey's motion.
- Simplify one part of the motion
Our lab uses a passive pendulum baseline. It leaves out active flicking, chemical attraction, silk extension, and glue deformation.
- Which line swings more slowly?
Keep swing energy and loss fixed. Compare short and long lines; count swings over the same interval before explaining your prediction.
Scientific sources and media credits
Mastophora hutchinsoni — Mastophora hutchinsoni ♀ (48448404301).jpg by Christina Butler, CC BY 2.0. Photograph fitted within the video without changing its composition; labels and animated diagrams added around it.
Script, diagrams, animation, and editing: WebTug, September 27, 2026. This video adaptation is available under CC BY-SA 4.0; individual photographs retain their credited licenses.
Watch the original publisher’s film for more detail
Machine job: Deliver glue to a flying moth at close range with a flexible, flicked line.
Force paths: Tension and motion travel along a single working line to a concentrated adhesive droplet. Chemical mimicry brings the moth into range; the mechanical event is a targeted swing and contact, not a large intercepting sheet.
Teaching model: A damped pendulum baseline θ″ = −(g/L) sin θ − c·θ′. Here the displayed c is a damping rate, with units of inverse time, rather than the translational damping coefficient in the orb equation. Primary research pointers: Yeargan on Mastophora hunting and Diaz and colleagues on bolas behavior and bioadhesives. The pendulum equation is an instructional analogy; neither citation makes it a complete model of the animal’s strike.
Limitation: Pendulum math ignores extensible silk, glue deformation, moth flight, and active leg control.
05 — Gumfoot tangle: ground contact coupled to a 3-D spring
Gumfoot: a trap that releases
Locate the release point and the stored energy in a cobweb system, then compare the lab's settling motion.
Jump to a chapter
Original WebTug explanation with animated teaching diagrams and credited still photographs. On-screen text carries the lesson; there is no audio narration.
Diagrams simplify the science. Animation timing and diagram dimensions are illustrative, not measurements of live spiders.
Compare gumfoot energy loss →Read the full transcript
- A tangle with a ground connection
This still photograph introduces a western black widow. Its cobweb strategy includes sticky gumfoot lines connecting the supporting web to the ground.
- An attachment designed to let go
In studied cobwebs, gumfoot attachments release more readily than scaffold attachments. A walking insect can trigger this ground connection to detach.
- The energy is already stored
The upper supporting silk holds elastic energy. After release, its recoil can pull the attached insect upward into the web.
- Follow the force through the web
The gumfoot strand connects prey to the support network. The scaffold supplies the spring action; the ground attachment provides the release point.
- One spring represents a whole tangle
Our vertical spring simplifies a three-dimensional web. The cited attachment study supports this strategy, without measuring our western widow model's forces.
- Which lift has less repeated motion?
Keep stored energy and scaffold stiffness fixed. Change only energy loss, replay the release, and compare how the upward motion settles.
Scientific sources and media credits
Latrodectus hesperus — Latrodectus hesperus (F Theridiidae).jpg by Marshal Hedin, CC BY 2.0. Photograph fitted within the video without changing its composition; labels and animated diagrams added around it.
Script, diagrams, animation, and editing: WebTug, September 27, 2026. This video adaptation is available under CC BY-SA 4.0; individual photographs retain their credited licenses.
Machine job: Catch prey that contacts vertical sticky lines and haul or lift them into an irregular support web.
Force paths: Adhesive gumfoot lines under tension connect ground-level contact to upper scaffolding. When a line detaches or yields at the foot, stored energy in the three-dimensional tangle can pull prey upward. Attachment discs and local silk junctions matter; this is a volume machine, not a flat sheet.
Teaching model: A single vertical spring metaphor a = (k·Δx − m·g) / m representing energy stored across supporting cobweb structure, with upward acceleration positive. Primary research pointer: Sahni and colleagues on cobweb attachment and gumfoot-related mechanics; UC IPM provides habitat context.
Limitation: The gumfoot strand alone is not treated as the sole energy store; the upper tangle shares the spring-like role.
06 — Dragline: safety, signal, and jump control
Draglines: control after takeoff
Distinguish observed jump stabilization from the lab's vertical fall analogy, then test the response after a line becomes taut.
Jump to a chapter
Original WebTug explanation with animated teaching diagrams and credited still photographs. On-screen text carries the lesson; there is no audio narration.
Diagrams simplify the science. Animation timing and diagram dimensions are illustrative, not measurements of live spiders.
Compare dragline settling →Read the full transcript
- A jumper with a silk connection
This still photograph introduces Hasarius adansoni. Before jumping, this spider attaches a dragline to its takeoff surface.
- Silk helps control body orientation
High-speed recordings showed draglines helping these spiders adjust body pitch in midair. The connection contributes to stable landing.
- A pull can change motion
Tension acts along the silk toward its anchor. Depending on its direction, that force can influence both movement and body rotation.
- Now isolate a vertical fall
In our lab analogy, gravity drives the fall. The safety line begins pulling only after it becomes taut and stretches.
- A simplification with a clear boundary
One spring and damper represent the loaded line. This vertical fall model does not reproduce a living spider's controlled jump.
- Which line settles with less bouncing?
Keep fall distance and stiffness fixed. Change energy loss, replay both settings, and compare repeated motion after the line becomes taut.
Scientific sources and media credits
Hasarius adansoni — Hasarius adansoni São Paulo.JPG by Leonardo Ré-Jorge, CC BY-SA 4.0. Photograph fitted within the video without changing its composition; labels and animated diagrams added around it.
Script, diagrams, animation, and editing: WebTug, September 27, 2026. This video adaptation is available under CC BY-SA 4.0; individual photographs retain their credited licenses.
Machine job: Arrest falls, transmit vibration, mark paths—or, in jumpers, help control pitch, deceleration, and energy dissipation during a leap.
Force paths: A major-ampullate line attached behind the body becomes taut under load. Tension redirects motion and dissipates energy once the line engages. This is usually not a prey-catching web; it is personal safety and control hardware.
Teaching model: After tautening, a linear spring–damper m·y″ = m·g − k·e − c·y′, where downward is positive and e is extension beyond the slack length. A physical tether cannot push: this approximation applies while tensile force remains positive; if the line goes slack, a separate slack phase is needed. Primary research pointer: Chen and colleagues on Hasarius jump-stabilizing draglines.
Limitation: Real dragline silk is nonlinear and depends on rate and humidity; the demo linearizes after engagement.
Comparing force paths at a glance
| Architecture | Who moves the structure? | Where energy is managed | Prey-catching? |
|---|---|---|---|
| Orb | Mostly passive until spider arrives | Shared across threads, especially load-bearing radii | Yes |
| Triangle | Spider preloads and releases | Stored elastic energy in sheet/anchor | Yes |
| Casting net | Spider throws the mesh | Stretch + strike timing | Yes |
| Bolas | Spider flicks the line | Line tension, swing, and adhesive contact | Yes (specialized) |
| Gumfoot tangle | Prey triggers line; web responds | 3-D scaffold + sticky feet | Yes |
| Dragline | Spider’s motion loads the line | Tension + damping in a tether | Usually no |
Architecture changes how force travels even when the proteins are cousins. That is the core WebTug teaching claim: material, structure, and machine are three stacked layers.
Ideal tether notes (and why Classic skips them)
A clean tethered-swing ideal begins with a taut massless line that constrains motion to an arc; release preserves instantaneous velocity into a projectile curve under gravity. The science-and-play guide develops the angular motion and tension formulas. In the ideal inextensible model, tension redirects the body without doing work along the constrained path. Real silk can stretch, dissipate energy, and go slack, so a spring-damper tether is a better next approximation than a rigid line.
WebTug deliberately uses neither swing model for play. Its one-button lift is an arcade teaching metaphor with transparent fixed accelerations. The architectures above live in the field guide and lab; the forest run keeps one readable control.
Trace a force path in a photograph
One contact, several routes to support
Start at an imagined prey contact on the orb photograph. Follow the local spiral to the nearby radii, then follow those spokes toward the frame and supporting vegetation. Some anchors are outside the crop; record them as unknown instead of assuming the visible edge is where the web ends.
Now look at the net-caster. Its front legs hold the mesh, and its body hangs from other support lines. A force on this net is coupled to an actively moving animal. That is a different boundary condition from a web fixed between plants.
Do not estimate spring stiffness from how straight a strand looks in a single picture. You would need scale, force, displacement, and an unloaded reference. The lab lets you vary a simplified stiffness deliberately; the photograph lets you inspect the architecture that the simplification leaves out.
How WebTug maps (and doesn’t)
Maps
- Six lab demonstrations mirror these six architectures with sources and limitations.
- Game profiles only change the silk-release drawing that hints at each machine.
- Homepage Chapter 05 language (“a web is more than its thread”) is the parent framing.
Doesn’t
- Playable WebTug is not an orb-impact simulator, slingshot simulator, or pendulum simulator.
- Forest trunks are score gates, not ecological anchors with compliance.
- Classic skins intentionally share gameplay rules and scoring. Separate science arcade games explore different silk mechanisms with their own controls.
Run the demos in the Spider Physics Lab. Compare the fixed arcade path in game physics and physics teaching vs WebTug.
Sources
- Sensenig et al. (2012): Spider orb webs rely on radial threads to absorb prey kinetic energy, Journal of the Royal Society Interface.
- Han et al. (2019): External power amplification drives prey capture in a spider web, PNAS.
- Stafstrom and Hebets (2016): Nocturnal foraging enhanced by enlarged secondary eyes in a net-casting spider, Biology Letters; University of Florida species account.
- Yeargan (1988): Ecology of a bolas spider, Mastophora hutchinsoni, Oecologia; Diaz et al. (2022): Behavior and Bioadhesives, Insects.
- Sahni et al. (2012): Cobweb-weaving spiders produce different attachment discs for locomotion and prey capture, Nature Communications.
- Chen et al. (2013): More than a safety line: jump-stabilizing silk of salticids, Journal of the Royal Society Interface.
- OpenStax University Physics: pendulums and damped harmonic motion — ideal-model background.
- Physics teaching versus the WebTug game and Spider Physics Lab evidence table — the site’s model choices and limitations.