How to Identify a Water Spider

Co-authored by Brandon Runyon

Last Updated: September 18, 2024 References

While other spider species live around or near water, the water spider (also known as the diving bell spider) is the only species that lives entirely underwater. Water spiders are able to survive because they carry around a bubble of oxygen that connects to their bodies. These spiders form underwater web structures that are full of tiny air bubbles, which help the spiders to stay underwater for over 24 hours before needing to resurface. Water spiders are found in Europe and Asia.

Method 1

Method 1 of 2:

Examining the Spider's Appearance

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1
Check that the spider is 10–15 mm (0.39–0.59 in) in length. Water spiders are very small and most individuals tend to be within this range. However, male water spiders have been found to be from 7.8 to 18.7 mm (0.31 to 0.74 in) and female spiders from 7.8 to 13.1 mm (0.31 to 0.52 in).^{[1]
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- Male water spiders tend to be larger than the females because males spend more time hunting, which requires greater strength to overcome the resistance of the water. On the other hand, females tend to spend more time maintaining their webs.
2
Look for a brown and velvety body. Water spiders have a head and thorax that is either light or dark brown. The abdomen tends to be dark brown and velvety in appearance.^{[2]
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- Sometimes water spiders can have a silvery appearance. This is because of the air bubble.
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3
Observe a large bubble that is connected to the spider. Water spiders have a large air bubble connected to their abdomen. This enables them to breathe underwater. The bubble is made from the air that is trapped in the tiny hairs that cover the spider’s legs and abdomen.
- The bubble stays connected to the spider for the whole time it is underwater, even while the spider is swimming and hunting.^{[3]
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Method 2

Method 2 of 2:

Observing the Spider's Environment and Behavior

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Geographically, water spiders are predominantly found in Central Asia, and Central and Northern Europe. You won't find water spiders in the USA, Canada, South America, Africa, or in the Pacific.^{[4]
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2
Check for a freshwater aquatic environment. Common habitats for water spiders include lakes, marshes, streams, ponds, and swamps. Water spiders tend to live in places where the water is slow-moving.^{[5]
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- Water spiders are particularly common in areas with a lot of aquatic vegetation.
3
See if the spider spends the majority of the day underwater. Water spiders are the only species of spider that live underwater. The spiders travel to the surface of the water approximately once per day for oxygen. All other activities, such as hunting and breeding, occur underwater.^{[6]
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- The bubble that is connected to the spider has nitrogen inside it which causes it to shrink over time. The spider will resurface to create a new bubble.^{[7]
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How do I get rid of water spiders?

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Take away or move the water, but beyond that, there isn't much you can do. If they're in your pool, you could add chemicals to the pool that could get rid of them.

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Do water spiders come into houses.

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Not usually. They would mostly just live in the water, as they don't need to come out of it.

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Water spiders feed primarily off crustaceans and aquatic insects. The spiders will hunt mayfly nymphs, phantom midge larvae, and water mites. To catch their prey, water spiders immobilize them using their venomous jaws.^{[8]
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Warnings

Despite being very small, water spiders can bite humans. Their venomous fangs can pierce through human skin, which can result in inflammation and sometimes a fever. Seek medical attention if you have any concerns.^{[9]
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