Silken Marvels: The Art and Science of Spider Web Engineering

Decoding the Complex World of Spider Webs and Their Multifaceted Uses

Spider webs have long captivated the human imagination with their intricate designs and remarkable structural properties. These delicate yet strong silk structures serve a variety of purposes for spiders, from prey capture to shelter and protection.

Gum-Footed Web (or messy webs): The Redback Spider’s Sticky Trap

The Redback Spider (Latrodectus hasseltii) constructs a distinctive web consisting of an irregular upper silk network with a closely woven, thimble-like retreat. From this upper network, vertical sticky catching threads, known as “gum-feet,” extend down to ground attachments. These webs can be found in a range of locations, such as among logs and rocks, grass tussocks, broad-leafed vegetables, and even in outside toilets and junk-piles.

The Redback Spider’s web is designed to maximize prey capture while providing a safe retreat for the spider. The upper network is usually built in dry, sheltered areas away from sunlight, while the sticky catching lines run down into open, more exposed areas. When an insect, spider, or even a small lizard walks into the “forest” of sticky lines, it becomes trapped. The spider then races down to deliver a quick bite and cover the struggling prey in bands of sticky silk, using a row of serrated bristles on the ends of its last legs, known as the “comb foot,” to rapidly pull the swathing silk from its spinnerets.

Platform Web: The Intricate Creations of Comb-Footed Spiders

Comb-footed platform spiders, such as Achaearanea mundula, are related to Redback Spiders but construct a different type of web. These non-dangerous spiders, common in bushland and gardens in eastern Australia, create moderately large and complex webs featuring a network of threads above a silk sheet, or “platform.”

When insects fly into the “knockdown” network of threads, they fall through onto the silk sheet below, where the spider seizes them. The spiders often use curled leaves or leaf fragments to create a loosely silked retreat in the center of the knockdown network, where they place their egg sacs.

Interestingly, these webs also harbor a range of other animals, from small moth larvae that scavenge along the silk lines to spiders that find prey in the outer parts of the web. One species, Argyrodes incursus, is a specialist predator that kills and eats the larger Achaearanea mundula, taking up residence inside the Platform Spider’s retreat and using it as a shelter for its own egg sacs.

Orb Webs: Efficient and Nearly Invisible Flying Insect Traps

Orb webs have evolved as an efficient means of capturing flying insects, providing a unique combination of large capture area and near invisibility. This makes detection and avoidance difficult for prey, especially at night when the web is only clearly visible when covered with dew. Orb webs require relatively little silk to build and can be completed quickly, which is important because many nocturnal orb weavers, such as Eriophora, destroy and eat (recycle) their webs toward dawn and must rebuild them each night.

Orb Spider webs

Building an orb web is a precise and intricate process that takes about 30 to 45 minutes. The spider uses air currents to waft the initial silk line across a gap in the foliage, creating a bridge line. It then moves back and forth across this line, strengthening it with more silk. From the bridge line’s center, the spider drops a vertical line to the ground, forming a basic Y-shaped framework. Supporting outer frame-lines and radial lines (the “spokes”) are then added, followed by a non-sticky, temporary spiral line laid down from the center outwards. This temporary spiral serves as a “scaffolding” for the spider to lay down the more closely spaced, permanent, sticky spiral from the periphery toward the center or hub. As the sticky spiral is laid down, the temporary spiral is removed and rolled up, with the excess silk being eaten and recycled by the spider.

Coastal Golden Orb weaver
Large Coastal Golden Orb weaver

Juvenile Webs: The St Andrew’s Cross Spider’s Defensive Strategy

The young of the St Andrew’s Cross Spider create a unique silk emblem at the center of their small orb webs. Instead of the diagonal cross seen in older spiders, they lay down a circular, lace-like pattern of zig-zag silk bands on which the spider sits. This pattern not only attracts small insects to the web but also provides an effective defense against predators. When disturbed, the spider can quickly slip through the web spiral and onto the other side of the silk pattern, disappearing from view.

This lace-like pattern in the web’s center is also typical of both young and adult Argiope trifasciata, another common species found throughout much of Australia and the western Pacific region.

Horizontal Line Webs: Simplicity and Effectiveness

Several unrelated spider species use single-line webs, strung either horizontally or at an angle, to catch their prey. Phoroncidia sp. (Family Theridiidae), tiny spiders found on low vegetation, bark, and leaf litter, spin a short, simple line of sticky droplets across a space and sit in wait, holding the line with a front leg. Small insects, especially flies, either hit or attempt to land on the sticky line and become stuck.

Miagrammopes sp. (Family Uloboridae) and the cribellate spiders of the genus Ranguma also have single-line webs. These stick-like spiders keep their single woolly silk line taut by pulling any slack silk into a loop underneath their body. When an insect hits the line of wool-like cribellate silk, the spider releases the loop of silk, which whips along the line to help tangle the prey.

Bolas Spider Webs: A Unique Hunting Strategy

Bolas Spiders, descended from orb web-weaving ancestors, have evolved a unique hunting method by greatly modifying their web. At night, these spiders emerge to hunt male moths, their only prey. They sit on a horizontal line and spin a short, single vertical line with a large dollop of sticky silk on its free end, resembling a fishing line with bait.

While waiting, the spider exudes an airborne scent (pheromone) that mimics the scent used by female moths to attract males. When male moths fly towards the spider, attracted by the false scent, the spider senses the vibrations of their wingbeats through its long, sensitive hairs. It then begins to swing the sticky bolas in a circle below itself. As the moth flies closer, it is hit by the bolas and covered in sticky silk. Coiled “reserve” silk within the bolas is paid out as the spider “plays” the moth, preventing the line from breaking. The spider then pulls the moth in, bites it, and begins feeding. The bolas line can be regarded as a highly modified remnant of an orb web.

Spider webs are a testament to the incredible adaptations and engineering prowess of these fascinating arachnids. From the sticky traps of Redback Spiders to the intricate platform webs of comb-footed spiders and the unique hunting strategies of Bolas Spiders, the diversity of spider webs is truly remarkable.

Spider Webs FAQs

Q: What are spider webs made of?
A: Spider webs are made of silk, which is a protein fiber produced by spiders. The silk is secreted as a liquid from special glands called spinnerets, located at the rear of the spider’s abdomen. As the liquid silk is drawn out, it hardens into a fine, strong, and elastic thread. Spiders use their silk for various purposes, such as building webs, wrapping prey, protecting eggs, and even as a means of transportation (known as “ballooning”).

Q: What are the 7 types of spider webs?
A: There are several distinct types of spider webs, each with its own unique architecture and purpose. The seven main types of spider webs are:

  1. Orb web: The most common and recognizable type of web, consisting of a circular frame with radial spokes and a spiral pattern.
  2. Tangle web or cobweb: An irregular, three-dimensional web with no distinct pattern, often found in corners of buildings or between branches.
  3. Sheet web: A flat, horizontal web with a funnel-like retreat at one edge, used by some spiders to catch falling insects.
  4. Funnel web: A flat, horizontal web with a funnel-shaped retreat at one end, used by some spiders to ambush prey.
  5. Tubular web: A tube-shaped web with a closed end, used by some spiders as a retreat and to capture prey.
  6. Triangle web: A triangular-shaped web with a single thread extending from the apex, used by some spiders to catch flying insects.
  7. Mesh web: An irregular web with a distinct sheet-like structure, used by some spiders to catch prey in low vegetation.

Q: What’s the difference between a spider web and a cobweb?
A: The terms “spider web” and “cobweb” are often used interchangeably, but there is a slight difference:

  • Spider web: This term refers to any type of web constructed by a spider, regardless of its shape or purpose.
  • Cobweb: This term typically refers to the irregular, tangled, three-dimensional webs often found in the corners of buildings, attics, or abandoned structures. Cobwebs are usually old, dusty, and no longer used by spiders.

Q: What are the 7 types of spider silk?
A: Spiders can produce up to seven different types of silk, each with unique properties and uses. The seven types of spider silk are:

  1. Dragline silk: The strongest and most versatile type of silk, used for the outer frame and radial threads of orb webs, as well as for “ballooning.”
  2. Minor ampullate silk: Similar to dragline silk but weaker, used for temporary scaffolding during web construction.
  3. Flagelliform silk: Highly elastic silk used for the capture spiral of orb webs, allowing the web to stretch and absorb the impact of flying insects.
  4. Aggregate silk: A sticky silk used to coat the capture spiral of orb webs, helping to retain caught prey.
  5. Tubuliform silk: A strong and tough silk used to construct egg sacs, providing protection for the spider’s eggs.
  6. Aciniform silk: A silk used to wrap and immobilize prey, as well as to reinforce egg sacs and construct retreat chambers.
  7. Piriform silk: A silk used to attach threads to surfaces and to form attachment discs, allowing spiders to move around their webs securely.

These silk structures not only serve as effective tools for prey capture but also provide shelter, protection, and even defense against predators. By studying the various types of spider webs and the behaviors associated with them, we gain a deeper appreciation for the complexity and ingenuity of these marvels of nature.

As we continue to explore the world of spider webs, we are sure to uncover even more fascinating insights into the lives of these incredible creatures and the vital roles they play in ecosystems around the globe.