The diving bell spider, Argyroneta aquatica, is the only known spider species that spends almost its entire life submerged underwater. This aquatic arachnid inhabits freshwater environments, including ponds, slow-moving streams, and marshes across parts of Europe and Asia. Its survival relies on the remarkable structure it builds: a silken web filled with air, which functions as an underwater home and breathing apparatus, known as the diving bell. Anchored to submerged vegetation, this bell allows the spider to live aquatically despite possessing book lungs designed for atmospheric oxygen.
Prey Found in the Water
The diving bell spider is an opportunistic carnivore, feeding primarily on small aquatic invertebrates that share its environment. Common prey items include tiny crustaceans, such as water fleas (Daphnia), and various insect larvae. They regularly consume mosquito larvae, phantom midge larvae, and mayfly nymphs, which are plentiful in slow-moving waters.
The spiders also prey on aquatic isopods, like Asellus aquaticus, and occasionally other small water spiders. Although less frequent, they will also strike at small fish or tadpoles if these vertebrates venture too close to the diving bell. The focus remains on securing small, easily subdued animals that populate the water column.
Hunting and Capture Techniques
The diving bell spider employs a sit-and-wait predatory strategy, using its silken home as a centralized hunting station. The spider spins silk lines that extend outward from the diving bell, anchoring them to nearby plants or debris. These threads act as trip wires, transmitting vibrations to the spider waiting inside.
When a potential meal brushes against the silk, the spider immediately detects the disturbance. The spider then rapidly darts out of the bell, moving quickly through the water to intercept the source of the vibration. It uses its legs to seize the prey and quickly injects venom through its fangs, which subdues and immobilizes the captured animal. Once the prey is secured, the spider transports it back to the safety of its air-filled refuge.
Eating Inside the Air Bell
The spider must bring its captured meal inside the diving bell for consumption. This is because, like most spiders, the diving bell spider cannot effectively feed underwater. The air-filled bell provides the necessary dry, atmospheric environment for the spider to begin its digestive process.
The spider uses external digestion, a method common across most arachnids. It injects digestive enzymes into the body of the prey, which break down the animal’s internal tissues. After the enzymes have liquefied the contents, the spider sucks up the resulting nutrient-rich slurry. The bell is essential not only for respiration but also as a secure, dry chamber for processing and consuming its prey.