i think its triggered by moving through multiple spawns, seeing i once triggered a spider after moving through 3 or 4 different areas

The only time I spawn a spider if when there's a war.
LOL

agreed, though it isn't just physical movement. I've noticed that moving in general causes a chance of a spider. for instance, I've spawned spiders warping to gates, dewarping, and leap frogging. which is why they spawn often on treks and in wars where there is a lot of movement. driving moves your spawn and acts like a warp even though you don't warp anywhere, so it gives a higher chance of it spawning one, since you don't do anything but sit there and "warp" continuously. also a reason why they spawn when you're grinding hard and moving around. they also seem to spawn more often when you come out of chat or cloud view while you're driving, which could be another factor. not certain on it yet. Just my observations.

First and last are true, thoough not totally sure about the second. Just today, a mage from a different bg spawned a spider, i hung out about 30 minutes later i spawned one, so not sure about the time intervals. Maybe different for each bg?