"There's a wasp in Australia that hunts spiders.
It doesn't eat them, though. It paralyses them, makes a little mud cocoon for each one, and before sealing it off, lays a single egg on the now trapped spider.
The egg hatches, the larva eats the still alive (and still paralysed) spider, and then breaks out of the cocoon as a wasp.
Turns out they're all over the world, not just Australia. If you see a wasp dragging a spider, that's what's going on."
the same way 85% of stats are figured.
BTW, Weedle s#cks @$$ in general as a Pokemon, as does its evolutions, so the fact that it can't learn anything "fancy", is not a problem. DO NOT waste your in-game time trying to get a great Weedle, FFS.