Daddy longlegs, aka cellar spiders.
I'm not sure but I believe these are "two-tailed spiders". Although they are arachnids, they are more closely related to scorpions. You can tell them apart from spiders since they have one body segment, as opposed to spiders that have two.
We mostly found them residing in tree hollows and saw a bobbing movement when disturbed. I read that on feeling threatened or feeling the slightest pressure, they're capable of discharging their leg and escaping the predator. At the loss of one (or more) legs, it can take them only less than a day to regain their stride!