The diving bell spider, Argyroneta aquatica, is the only spider known to live almost its entire life underwater. Native to freshwater habitats across Europe and Asia, it appears mid to dark brown out of the water. Once submerged, it takes on a silvery appearance caused by a thin layer of air trapped by dense, water-repellent hairs covering its abdomen and legs.
The Underwater Diving Bell
The spider’s name comes from its underwater home. To build it, the spider spins a dense, sheet-like web of silk and anchors it to underwater plants. The spider then makes numerous trips to the surface to collect air.
It traps air bubbles using specialized hairs on its abdomen and legs. Holding the bubble with its rear legs, it swims down and releases the air underneath the silk sheet. Repeated trips gradually fill the web, inflating it into a dome-shaped chamber resembling a historic diving bell, where the spider can rest, molt, and consume prey.
This underwater bell functions as a physical gill. Oxygen from the surrounding water diffuses into the bell, while carbon dioxide from the spider’s respiration diffuses out. This gas exchange allows the spider to remain submerged for long periods, often only needing to surface once a day to replenish its air supply.
Habitat and Hunting
The diving bell spider is found across Europe and parts of Asia in clean, slow-moving or still freshwater bodies like ponds and streams. These environments must have abundant aquatic vegetation, which provides the anchor points for its underwater web.
As a predator, it waits inside or near the entrance of its diving bell to ambush prey that swims or drifts too close. Females spend most of their time within their bells, darting out to capture animals that touch the structure or its anchoring silk lines.
Its diet consists of small aquatic invertebrates, including mosquito larvae, small crustaceans, and water mites. After capturing its meal, the spider returns to its bell to feed. While most consumption happens underwater, it sometimes brings prey to the surface.
Reproduction and Bite
The reproductive cycle occurs almost entirely underwater. The male, often larger than the female, builds a smaller bell near a female’s. He then spins a tunnel from his bell to hers to mate inside her larger structure, which also serves as a nursery.
After mating, the female produces an egg sac with 30 to 70 eggs, securing it inside her bell. She guards the cocoon until the spiderlings hatch weeks later. The young spiders remain with their mother for two to four weeks, molting several times before dispersing to build their own underwater homes.
The bite is painful, often compared to a bee sting, and can cause localized inflammation. The venom is not medically significant to people, as its function is to subdue aquatic prey.