[Jetrel]

Spiders are actually a really good example of this principle.

What's really interesting here is the problem of just a "naive threat estimation", which usually is always just estimating the purely mechanical danger the body of a foe could pose. We have a healthy respect for large animals like horses and cattle that could crush us. We've got an open fear of predators with obvious sharp teeth and such (wolves, big cats, crocodilians). But bugs? Bugs are really weird because they're not mechanically dangerous, and as, say, a child, sizing them up, there's no sensible reason to be scared.

I find it really interesting how - even without necessarily understanding that they've got poison, we as a species do a really good job of being scared of "things that aren't visually obvious threats" like this - especially in kids, who really struggle to "get it" when it comes to what's actually dangerous about, say, a spider or a jellyfish.

I think you really hit on something there - I think a little bit of it is actually a built-in instinctual fear, but there's also a huge part that's an imitative fear kids pick up from anything that the body language of a parent conveys as dangerous.