Araneidae
Common Name
Orb-weaver spiders
Overview
The family Araneidae, commonly known as orb-weaver spiders, comprises a significant portion of all spider species. They are renowned for their wheel-shaped, intricate webs that are both functional and mesmerizing. These spiders are found on every continent except Antarctica, in a range of habitats from tropical rainforests to temperate forests and grasslands.
Taxonomy
Key Characteristics
- Orb-weaver spiders possess eight eyes arranged in two rows.
- They have robust, often brightly colored bodies.
- Their third pair of legs is specially adapted to handling silk during web construction.
- They create large, circular webs made of sticky silk.
- Many species exhibit sexual dimorphism, with females often much larger than males.
Life Cycle
- Egg Stage : Eggs are laid in silken sacs and often attached to foliage.
- Spiderling Stage : Spiderlings hatch from the egg sacs and are miniatures of the adults. They disperse through a process called ballooning, where they use silk threads to catch the wind.
- Juvenile Stage : Juveniles undergo several molts as they grow.
- Adult Stage : Adults reach maturity after a series of molts. Mating occurs, and the cycle begins anew.
Behavior and Ecology
- Orb-weaver spiders are primarily nocturnal and construct their webs at night.
- Their webs are used to capture flying insects, which are then wrapped in silk and consumed.
- They play a critical role in controlling insect populations.
- Males often approach females cautiously for mating, sometimes using vibrations to signal their presence.
Notable Species
- Argiope aurantia (Yellow garden spider)
- Araneus diadematus (European garden spider)
- Gasteracantha cancriformis (Spiny orb-weaver)
- Nephila clavipes (Golden silk orb-weaver)
Conservation
Most orb-weaver species are not endangered and are common in their respective habitats. However, habitat destruction and pesticide use can impact their populations.
Significance to Humans
- Orb-weaver spiders contribute to pest control by preying on insects.
- Their webs have been studied for their remarkable structural properties and are of interest in materials science.
- They are often subjects of fascination due to their visual appeal and web-building skills.
Fun Facts
- Orb-weaver spiders can rebuild their webs daily, typically consuming the old web before constructing a new one.
- The silk of some orb-weavers can be more than five times stronger than steel of the same diameter.
- Some orb-weavers add stabilimenta (zigzag patterns) to their webs, which may reflect ultraviolet light to attract prey or serve as a warning to larger animals to avoid the web.
- The golden silk produced by Nephila species appears golden in natural light and can attract pollinators into the web.