Spiders do not build nests like birds do for continuous habitation. Instead, these arachnids use extruded silk fibers to create specialized structures for different biological functions. The question of whether a spider builds a nest is better answered by understanding the diversity of silk-based constructions, which serve as permanent residences or temporary hunting traps. The function of a silk structure dictates its form, material, and placement, proving that a single web is only one part of a spider’s engineering repertoire.
Defining Spider Retreats
The silk structures that function most like a permanent home are called retreats. These serve as a protective domicile for resting, molting, and protection from predators or harsh weather. Terrestrial species like tarantulas and trapdoor spiders line their underground burrows with silk to stabilize the soil walls, preventing collapse and facilitating easy movement up and down the tunnel. These silk-lined burrows are long-term residences where the spider spends most of its life, distinct from hunting webs.
Other spiders construct silken sacs or tents within sheltered environments, such as curled leaves, under bark, or in rock crevices. These structures provide a safe, enclosed space for the vulnerable process of molting, when the spider sheds its hard exoskeleton. Funnel-web spiders weave a silk sheet on the ground that leads into a narrow, silk-lined tube, or funnel. This funnel is the actual retreat where the spider waits, maintaining a controlled microclimate for insulation and humidity control.
The Function of Hunting Webs
The most recognizable silk creations are hunting webs, built primarily as external tools for prey capture, distinguishing them from permanent retreats. The iconic orb web, spun by garden spiders, is a flat, circular structure composed of a non-sticky frame and radial spokes, with a spiraling capture thread coated in minute droplets of sticky glue. These webs are highly efficient, using the silk’s elasticity and strength to absorb the impact of flying insects and hold them fast.
Other species employ different geometric designs to suit their environment and prey. The flat, horizontal sheet web acts like a trip hazard for walking insects. Tangle webs, or cobwebs, are three-dimensional snares consisting of a chaotic maze of fine, non-sticky threads that disorient and trap prey, causing them to fall into a lower sheet or a gum-footed thread. Some specialized hunters, like the bolas spider, swing a single line tipped with a sticky silk ball infused with a pheromone to lure in male prey. These hunting structures are often temporary, consumed and rebuilt daily or nightly to maintain their sticky effectiveness.
Silk Structures for Reproduction
Silk plays an indispensable role in protecting the next generation through the construction of the egg sac, often called a cocoon. The female creates this structure by spinning a silk pad, depositing the eggs, and then wrapping them in multiple layers of specialized, dense silk for insulation and protection. The final sac can be spherical, teardrop-shaped, or disk-like, and some species incorporate debris or plant matter into the outer layer for camouflage.
The number of eggs within a single sac can range from a few to over a thousand, depending on the species. Maternal care varies significantly. Some females abandon the sac after construction, while others, like wolf spiders, carry the sac attached to their spinnerets, instinctively turning it to prevent the eggs from deforming. Other species, such as the European cobweb spider, construct a silken thimble and actively move the egg sac in and out of it to regulate the temperature of the developing embryos.