Orb weaver spiders are a common group of arachnids, known for the intricate webs they construct. They inhabit diverse environments, from gardens to forests, where their large, conspicuous webs are often seen. Their name reflects a key characteristic.
The Defining Orb Web
The name “orb weaver” refers to the distinctive, circular web these spiders build. An orb web is a two-dimensional, wheel-shaped structure with radial threads extending like spokes from a central hub. These non-sticky radial lines provide the web’s structural support and serve as pathways for the spider. Interwoven with these radial threads is a spiral of sticky capture silk, designed to ensnare flying insects. The term “orb” itself means circular, precisely describing the geometry of these remarkable webs.
Orb web construction begins when the spider releases a silk line carried by the wind until it attaches to a distant support. Once secure, the spider reinforces this line and drops another, often forming a “Y” shape for the web’s foundation. Non-sticky radial spokes are then added, radiating from the central hub to the outer frame. Finally, the spider lays down the sticky capture spiral, starting from the outside and working inward, often replacing a temporary, non-sticky spiral used during construction. This methodical process creates an efficient trap for airborne prey.
Characteristics of Orb Weavers
Orb weaver spiders belong to the family Araneidae, a group with over 3,000 species globally. They exhibit varied appearances; many common species have stout, rounded abdomens, sometimes with spines or distinctive patterns. Their legs are hairy or spiny, assisting them in manipulating silk and navigating webs. They possess eight eyes, usually in two rows, but their eyesight is poor.
Due to poor vision, orb weavers rely on vibrations detected through their webs to perceive surroundings and locate prey. Many species are nocturnal, building or repairing webs at night. They often consume much of their web’s silk at dawn, potentially to regain moisture and prevent larger animals from becoming entangled. While the common name “orb weaver” broadly refers to any spider that constructs a circular web, the scientific classification within the Araneidae family encompasses the vast majority of these well-known web builders.
Life and Hunting Strategies
Orb weavers utilize their meticulously constructed webs as their primary tool for survival, functioning as passive traps for prey. When an insect flies or walks into the sticky threads, its struggles create vibrations that travel along the silk strands to the spider. The spider, often waiting at the web’s center or in a nearby retreat connected by a signal line, quickly detects these vibrations, which guide it to its entangled meal.
Upon reaching the prey, the orb weaver typically immobilizes it with a venomous bite and then wraps it in silk, either for immediate consumption or to store for later. Their diet largely consists of small insects such as flies, moths, and mosquitoes, though larger orb weavers can occasionally capture small frogs or even hummingbirds if they become ensnared. Orb weavers are found in various habitats where there is abundant prey and suitable anchor points for their webs, including gardens, fields, forests, and around human structures. Most orb weavers have a lifespan of about 12 months, with females laying eggs in a silken sac before dying, and spiderlings dispersing to build their own tiny webs. Many species rebuild their webs daily, ensuring their hunting apparatus remains effective.