Trapdoor spiders, belonging to the infraorder Mygalomorphae, are a specialized group of arachnids defined by their unique, sedentary lifestyle. Unlike web-building spiders, they spend most of their lives within a single subterranean dwelling. This burrow is not merely a shelter; it is a precisely engineered hunting apparatus that dictates their method for obtaining sustenance, making the feeding process an exercise in patience and explosive speed.
Anatomy of the Hunting Burrow
The hunting burrow is an underground tube that serves as both the spider’s home and its predatory tool. The tunnel is typically lined with silk, which stabilizes the soil walls and prevents collapse, with burrows reaching depths of up to 40 centimeters in some species. The silk lining also transmits ground vibrations up to the spider waiting inside.
At the surface, the burrow is sealed with the structure that gives the spider its name: the trapdoor. This lid is composed of a mixture of silk, soil, and vegetation, rendering it highly camouflaged and nearly invisible when closed. Most trapdoors are hinged on one side with silk, allowing the spider to quickly flip it open and closed during an attack, which helps the ambush predator surprise its prey.
Primary Prey and Diet Composition
Trapdoor spiders are generalist carnivores, feeding on a wide variety of small creatures that venture close to their burrow entrance. The bulk of their diet consists of ground-dwelling invertebrates, primarily insects like crickets, moths, grasshoppers, and beetles. They also consume other arthropods, including ants, millipedes, and other spiders.
The size of the spider directly influences the prey it can subdue. Larger species may occasionally capture small vertebrates such as frogs, lizards, or mice if the opportunity presents itself near the burrow opening. However, the prey must be small enough to be quickly overpowered and dragged back into the narrow tunnel.
Ambush Hunting Mechanics
The hunting process begins with the spider positioning itself just inside the trapdoor, often holding the lid closed with its chelicerae or legs. The first phase is sensing, where the spider uses sensitive hairs on its legs and pedipalps to detect vibrations moving through the soil or the burrow’s silk lining. Some species extend fine silk strands, known as trip lines, radiating out from the entrance to widen the detection field for passing prey.
These vibrations communicate the presence, size, and location of a potential meal moving across the surface. The spider waits patiently for the ideal moment, typically under the cover of darkness when they are most active. Once a suitable target is detected, the strike is initiated with speed and precision.
The spider flings the camouflaged lid open and lunges out of the burrow. It seizes the prey with its downward-facing fangs, quickly injecting venom that subdues the victim. The entire sequence, from lunge to capture, takes only a fraction of a second. The spider then rapidly retracts into the safety of its tunnel, dragging the prey behind it before sealing the trapdoor once more.
Post-Capture Feeding Process
Once the prey is secured within the burrow, the spider begins external digestion. The spider’s venom often contains components that start to break down the prey’s internal structures. Following the venom injection, the spider releases digestive enzymes, including proteases and lipases, into the prey’s body.
These enzymes liquefy the soft tissues, turning the internal contents into a nutrient-rich broth. The spider then uses a muscular sucking stomach to draw the liquid nutrition into its gut, often periodically regurgitating and re-sucking the mixture to maximize digestion. This process leaves behind the empty exoskeleton, which the spider pushes out of the burrow entrance to maintain cleanliness.