Orb weaver spiders are common arachnids recognized for their intricate, wheel-shaped webs. These spiders are found globally, inhabiting gardens, fields, and forests, as well as areas around human structures. They play a role in various ecosystems as predators, primarily capturing flying insects. Their feeding habits are closely tied to their web-building behavior.
Primary Prey
Orb weaver spiders are generalist predators, primarily feeding on common flying insects such as flies, moths, beetles, wasps, and mosquitoes. These prey items are abundant in the environments where orb weavers build their webs, making them readily available food sources.
The size of the prey can vary, with orb weavers capable of capturing anything from a small mosquito to a larger butterfly. In some instances, larger orb weaver species have even been observed to trap and consume small frogs or hummingbirds that become entangled in their substantial webs. While insects form the majority of their diet, some studies indicate that juvenile orb weavers may also consume pollen, which can constitute about 25% of their diet, supplementing their insect-based meals.
Webs as Hunting Tools
The iconic orb web serves as the primary tool for orb weavers to capture their food. This web is a complex structure typically composed of non-sticky radial spokes and a sticky spiral capture thread. The spider initially constructs the non-sticky framework, then adds the sticky spiral, which is coated with adhesive droplets designed to ensnare prey. Many orb weavers construct a new web daily, often at night, and may even consume the old web to recycle silk proteins.
Once an insect becomes entangled in the sticky threads, its struggles create vibrations that travel through the web. Orb weavers, possessing poor vision, rely on these vibrations, detected through sensitive organs on their legs, to locate their prey. Upon detection, the spider quickly approaches the trapped insect, bites it to inject venom that paralyzes it, and then wraps it tightly in silk. This wrapping prevents the prey from escaping and secures it.
Dietary Adaptations and Variations
An orb weaver’s diet can show variations influenced by factors such as its life stage, species-specific preferences, and environmental conditions. Younger spiders, or spiderlings, typically consume smaller prey items, and pollen can be a significant part of their diet when insect prey is less available.
Different species of orb weavers may exhibit preferences for certain types of insects based on web design and habitat. For example, some species found in rice fields primarily catch Lepidoptera, Diptera, and Homoptera. Once prey is captured and secured, orb weavers consume their meal through external digestion, injecting digestive enzymes to liquefy internal tissues and then slurping the resulting liquid, discarding indigestible solid parts.