Today’s post is about a particularly interesting species of spider. As I said before, I’m terrified of spiders. So I hope you’ll appreciate how difficult this entry was to write. Especially finding the pictures. That part is always the worst when it comes to spiders. But, as I also said before, spiders are some of the most innovative and fascinating groups of animals. So I will continue to include them in my blog. Even though looking at a picture of one makes my skin crawl.
The water spider is described fairly well by its name; it lives its entire life under water. This spider is the only spider in the world that does this. You see, spiders aren’t exactly designed in to live in water. Like us, they breathe air. So what does this little spider do to stay alive underwater? Does it have gills, like fish? Or does it have to come to the surface every time it needs a breath, like a whale? It does neither. Instead, the water spider uses the feature most associated with spiders to survive in its difficult environment. To breathe underwater, the water spider simply builds a web.
The water spider is known by another name: the diving bell spider. This spider constructs an underwater structure out of web in which to live. The web is what gives the spider the name ‘diving bell spider’. The spider swims to the surface to collect air with which to fill its ‘diving bell’. Bubbles form on the hairs on the spiders legs and abdomen, allowing it to fill the diving bell and swim outside of the bell for short periods of time. Despite what you might think, the spider doesn’t have to refill its home very often. This is because in well-oxygenated water, diffusion maintains an ideal concentration of oxygen inside the bell.
Diffusion is the movement of a gas from an area of high concentration to an area of low concentration. Every gas will move to the lower concentration area every time; think of the smell of food wafting through a house. As the spider sits in its bell, it breathes in oxygen and expels carbon dioxide. When the concentration of oxygen in the bell reaches a level below that of the surrounding water, oxygen diffuses in, replenishing the spider’s air supply.
Female water spiders spend most of their lives inside their webs, only coming out to hunt. Insects that touch the diving bell or its supporting strings are quickly bitten with the water spider’s venomous bite and dragged back inside the bell for a feast. Male spiders behave a bit differently, building smaller webs and hunting more actively. They usually attach a thin silken thread to a plant and move through the water that way, as swimming can be difficult with bubbles all over your body
When the male spider is ready to mate, he builds a new bell next to the female’s and then constructs a tunnel to her web. After forcing his way into her bell, the two spiders mate. It seems like a bit of an invasion of privacy to me, but that’s the way them spiders get things done, I guess.
Water spiders have evolved an amazing way of living in an environment inhospitable to all other spiders. As much as I admire them for that, I’d still probably kill one if I saw it. Or run away screaming. One of the two. In any case, I won’t be swimming in any ponds in Europe or northern Asia (where they live). Anyway, enough about my arachnophobia. Thanks for reading, and have a great day!
Cover image By Baupi, CC BY-SA 3.0