Garden spiders, commonly recognized as the large, web-spinning arachnids found in backyard habitats, belong primarily to the orb-weaver family, Araneidae. These creatures are widespread and often noticed due to the large, intricate webs they construct between plants and structures. Like all spiders, they are predatory carnivores whose diet is central to their survival and their classification within the class Arachnida.
The Typical Diet: Insect Pests
Garden spiders are opportunistic feeders that primarily consume flying insects snared in their expansive webs. Their diet is largely dictated by what arthropods encounter their silk traps. Prey items frequently include mosquitoes, house flies, and various moths, which are easily subdued once entangled in the sticky threads. They also routinely capture larger garden pests such as grasshoppers, beetles, and wasps. The size of the prey is limited by what the spider can quickly immobilize and wrap before it escapes or causes damage to the web.
Prey Capture: Web Construction and Silk Use
The garden spider’s entire hunting strategy revolves around the construction and maintenance of its orb-shaped web. This web is a complex structure utilizing several varieties of silk produced by different spinnerets. The radial spokes and frame lines are composed of strong, non-sticky dragline silk, providing structural support and acting as signal lines. The spiral threads are coated in a specialized, adhesive fluid that physically traps flying prey upon contact. The spider waits patiently at the hub or a nearby retreat, holding a signal line to detect vibrations in the web, then rushes out to deliver a paralyzing bite of venom and tightly wrap the struggling victim in non-sticky silk.
The Unique Process of External Digestion
Spiders possess a narrow gut that prevents them from swallowing solid food particles. To overcome this limitation, garden spiders employ external, or extra-oral, digestion. After the prey is wrapped in silk, the spider injects a cocktail of digestive enzymes, which may be mixed with its venom, directly into the victim’s body. These enzymes, which include proteases, lipases, and nucleases, begin to break down the prey’s internal tissues, liquefying the contents while still inside the exoskeleton. The spider then uses its powerful sucking stomach to ingest the resulting liquid meal, leaving behind the hollow, dry shell of the victim.
Ecological Impact: Natural Pest Control
The predatory activity of garden spiders makes them beneficial residents in any outdoor ecosystem. By specializing in the capture of flying insects, they naturally regulate populations of arthropods that can damage plants or bother humans. This helps maintain a healthy balance in the garden, often preventing pest outbreaks. Their presence provides an effective, chemical-free method of insect management for gardeners and homeowners. A single large orb-weaver can capture hundreds of insects over a season, significantly reducing the pressure from crop pests.