Many people associate spiders with dry, dusty corners or intricate webs. However, certain spider species have remarkable adaptations that allow them to thrive in aquatic environments. These spiders exhibit a range of behaviors, from gliding across the water’s surface to actively diving and living for extended periods submerged. Their ability to interact with water demonstrates a fascinating evolutionary versatility within the arachnid world.
Spiders that Walk on Water
Some spiders possess the ability to move across the surface of water, primarily utilizing its surface tension. Fishing spiders, belonging to the genus Dolomedes, are well-known examples. These spiders have specialized, water-repellent (hydrophobic) hairs on their legs that help them distribute their weight and prevent them from breaking the water’s surface film. This allows them to effectively “skate” across ponds and streams.
When sensing vibrations from prey or disturbances, fishing spiders quickly dart across the surface to capture insects or even small fish. Some wolf spiders, such as Pardosa purbeckensis, also demonstrate this capacity, running across the surface of salt marshes and mud flats. Longjawed orbweavers are another group that can run across the water’s surface if they happen to fall in, using similar principles.
Spiders that Dive Underwater
While some spiders walk on water, others take their aquatic adaptations further by actively submerging themselves. The diving bell spider, Argyroneta aquatica, is unique for spending nearly its entire life underwater. This species constructs a bell-shaped web anchored to underwater plants, which it inflates with air brought from the surface. The spider traps air bubbles in the fine hairs on its abdomen and legs, appearing silvery as it transports them to its retreat. Inside this “diving bell,” the spider can breathe, consume prey, mate, and lay eggs, only briefly surfacing to replenish air supply.
Other spiders, including some Dolomedes species, can temporarily submerge themselves by encasing their bodies in an air bubble, often remaining underwater for several minutes to avoid predators. Certain intertidal spiders, like Desis marina, create watertight silk nests in submerged areas, emerging only during low tide to hunt.
Reasons for Aquatic Behavior
The reasons behind these spiders’ aquatic behaviors are diverse, primarily revolving around survival and resource acquisition. Many aquatic spiders use water as a hunting ground, preying on aquatic insects, their larvae, or even small vertebrates like tadpoles andtherners. Aquatic environments also offer refuge from land-based predators. If threatened, many water-adapted spiders will quickly dive beneath the surface, hiding there until the danger has passed.
Water can also serve as a means of dispersal, allowing younger spiders to move to new habitats by floating or swimming away from crowded areas. This ability to exploit both terrestrial and aquatic niches expands their ecological opportunities.
Where You Might Find Them
Fishing spiders and other surface-dwelling species are typically found near ponds, slow-moving streams, wetlands, and damp areas with abundant aquatic vegetation. They might be seen resting on plants at the water’s edge, with their front legs extended onto the surface, ready to detect prey. The diving bell spider, Argyroneta aquatica, inhabits clean freshwater bodies with minimal flow, such as ponds, canals, and marshes, particularly where aquatic plants are plentiful.
Most aquatic spiders are generally harmless to humans. Although the bite of a diving bell spider can be painful, similar to a bee sting, they are not typically aggressive unless mishandled.