Diving bell spider

Lore & Background

A. aquatica is found in clean freshwater habitats with aquatic vegetation, such as lakes, ponds, canals, marshes and slow-moving streams. It ranges through much of mainland Europe (no records from Portugal, though it is recorded from Greece and Albania), the British Isles and central to northern Asia ranging as far south as Iran and as far north as Siberia, up to latitude 62°N. Most of the range is inhabited by the nominate subspecies, but Japan has its own subspecies, the very similar A. a. japonica. South Korea has a protected area, Yeoncheon Eundaeri water spider habitat, for this species, which is listed as Least Concern globally by the IUCN but is of conservation concern in that country. As with other spiders it breathes air; when submerged in water, an air bubble is trapped by a dense layer of hydrophobic hairs on its abdomen and legs, giving the abdomen a silvery appearance. The spider lives for about two years in captivity. A. aquatica is able to remain submerged for prolonged periods of time due to the silk-based structure it constructs in order to retain an oxygen supply, named after the diving bell structure it resembles. The species range in size, although the size of females may be limited as they put more energy into building and maintaining their larger bells. Males are more active and on average almost 30% larger than females, measuring 10–15 mm in head-and-body length compared to 8–12 mm. This size differential favoring males is unusual for spiders, where sexual dimorphism is usually in favour of larger females. The spiders prey on aquatic insects and crustaceans such as mosquito larvae and Daphnia. The spiders themselves fall prey to frogs and fish. Their bite is often described as being very painful to humans and as causing localised inflammation, vomiting, and slight feverishness that disappears after 5–10 days. However, solid evidence is lacking, with information being based on old and unverified reports because recent confirmed and published reports are lacking, leading some sources to refer to its bite as reputedly painful.

Reader's Guide

The diving bell spider is significant as the only spider species that spends almost its entire life underwater, including resting, catching and eating prey, mating, egg laying, and overwintering. It only briefly surfaces to replenish its oxygen supply. Its diving bell—a silk structure inflated with air from the surface—allows gas exchange with the surrounding water, functioning as an inorganic gill. This adaptation has been studied for insights into underwater respiration and material science. The species also exhibits reversed sexual size dimorphism, with males being larger than females, which is unusual among spiders. Its conservation status is notable in South Korea, where a protected area exists for this endangered species. The spider's unique biology continues to inform understanding of arachnid evolution and adaptation to extreme environments.

Did You Know?

• The diving bell spider is the only known spider that spends almost all its life underwater.
• Males are on average almost 30% larger than females, which is unusual for spiders.
• The spider's bite is reputedly painful, but recent confirmed reports are lacking.
• South Korea has a protected area, Yeoncheon Eundaeri water spider habitat, for this species, which is globally listed as Least Concern.

Taxonomic Standing and Global Reach

The diving bell spider belongs to one of the most species-rich lineages on Earth. Spiders constitute the largest order within the arachnids and rank seventh in total species diversity across all biological orders. Their geographic range is essentially planet-wide: spiders have established themselves on every continent except Antarctica and occupy nearly every terrestrial habitat known to science. Despite this breadth, the very scaffolding of spider classification remains contested. For the diving bell spider, this means its precise placement within the broader araneoid tree is part of a living, debated conversation rather than a settled fact.

Body Architecture and the Chelicerate Blueprint

Like all members of order Araneae, the diving bell spider is built on the chelicerate body plan, which sets it apart from insects and other arthropods. Its body is fused into two major tagmata: the cephalothorax, or prosoma, at the front and the opisthosoma, commonly called the abdomen, at the rear, linked by a small cylindrical joint known as the pedicel. Notably, spiders lack antennae entirely; the first appendages ahead of the mouth are a pair of two-segmented chelicerae tipped with venom-delivering fangs, while the pedipalps behind the mouth serve in feeding and other roles. Unlike insects, spiders possess no extensor muscles in their legs and instead extend them using hydraulic pressure. In all but the most primitive suborder, the Mesothelae, the nervous system is highly centralized, with every ganglion fused into a single mass within the cephalothorax. The very terms cephalothorax and abdomen are debated by some anatomists, since no paleontological or embryological evidence confirms a separate thoracic division ever existed in spider ancestors, and the opisthosoma houses the heart and respiratory organs, structures atypical of a true insect abdomen.

Silk, Spinnerets, and a Four-Hundred-Million-Year Thread

The silk-producing apparatus is among the most remarkable features inherited by the diving bell spider from its araneoid ancestors. The opisthosoma bears spinnerets, modified appendages that extrude silk from as many as six distinct gland types, each yielding fibers with different mechanical properties. Spider webs across the order vary enormously in size, architecture, and the proportion of sticky thread employed. Current evidence suggests the spiral orb web may represent one of the earliest web designs, while tangled cobweb producers are actually more abundant and diverse than their orb-weaving counterparts.

Predation, Courtship, and the Social Spectrum

Capture strategies range from sticky-web trapping and sticky bolas lassoing to prey mimicry and outright pursuit. Most spiders locate their meals through vibration sensing, though active hunters rely on sharp vision, and the genus Portia displays what researchers interpret as genuine tactical intelligence. Because their guts are too narrow for solid food, spiders flood prey with digestive enzymes and grind material using the bases of their pedipalps. Mating presents a grave risk: females are typically much larger and may consume males, so courtship involves elaborate identification rituals. Females spin silk egg cases holding hundreds of eggs, and many species actively guard or feed their young. Most spiders live no more than two years, though mygalomorphs can exceed twenty.