This little orbweaver was just sitting innocently in her web, and I don’t know how they do it.
The thing is, when they’re on that web and the wind is blowing, they’re just vibrating all over the place. You’d think they’d be hopelessly motion-sick.
I couldn’t stand it so I let her take a break from the gale on my finger.
Don’t worry, I returned her to the same branch.
I’d imagine they lack our vestibular system and are adapted to chilling on their webs riding out rough winds?
Exactly what Hemidactylus@1 said!
Remember, that to the very small (spiders, insects, single celled organisms, etc.) gravitational acceleration is not even recognized. Being upside down or at any other arbitrary rotational orientation just rotates their field of vision (when they even have that), and nothing else. They are unlikely to have any sense of a global up and down, those directions are all always relative to them. As you surely know, some spiders have learned to emit silk strands downwind and then to ride them to more distant locations, surfing the air currents.
Correct me if I’m wrong, but our sense of balance/orientation/motion comes from our ears. Do spiders have ears?
Robert79@3:
The vertebrate vestibular system is located in the inner ear. Some creatures could conceivably have ears without the vestibular system, but all vertebrates have that combination. Invertebrates lack any vestibular system, and some are also deaf as well, but hearing and the vestibular system are only common in vertebrates.
To address your question more directly, spiders sense vibrations with specialized hairs on their legs, so that takes the place of “ears”. If your air vibration detection system was located in your knees (without any vestibular system), would you call your knees your “ears”? “Ears” in vertebrates mean something quite different from the invertebrates.
https://en.wikipedia.org/wiki/Vestibular_system