Many times spirits will be able to see into the future a little ways, some will be able to see far - and some can see only a few hours ahead.
When something bad is about to happen, spirits will converge. I have witnessed it first hand, and found it to be an absolutely beautiful and magnetic thing to see - and believe that other psychics are also drawn to these convergences. Non-sensitives can also be drawn to these places as well, like moths to a flame.. and speaking of Moths, the Mothman is a phenomena that may be related to this. The Mothmen COULD have something to do with that convergence of spirits, they could be clumps of spiritual manifestation, as my theory goes.
When more than one spiritual manifestation occurs (when spirits cross from the spiritual dimension to more human-sensitive planes, using ambient or human bodily energy, or using a multi-spiritual synergy created by the convergence of several spirits) there is sometimes a strange melding that occurs. For example: if your Uncle Billy who has blue eyes and white hair with a dragon tattoo on his back comes to visit me at the same time as your Aunt Milly who has brown hair and grey eyes - I will sometimes see the spirit with one blue eye, one grey eye, or rapidly shifting colours, with half grey and half brown hair, and a phasing dragon tattoo - that is both male and female. I can tell if it's two spirits in one, usually, but it's harder to tell if there's four instead of ten, if you know what I mean.
What am I getting at?
Sometimes hundreds of spirits get together and start to look VERY unusual - monstrous even. Perhaps the Mothman is a combination of spirits clumping together to pool their power and warn the masses more tangibly. I'm not sure if they are working together, but I think they do. This multi-spirit being can take on an energy of its own, and it no longer sounds or acts completely human in it's worry. They also look scarier and act scarier to try and scare you silly into vacating the area.
So what do you do if you see this clumped spirit, or get a phone call that knows you're hiding chapstick in your hotel nightstand? (I loved that movie) Well, as in the movie, clumping spirits are trying to get you to leave, they're trying to scare you out of the area. Sometimes you have months to prepare, sometimes only days or hours. What's best is to leave town if you see a true Mothman.
Have I seen a Mothman? No, but then again I see deceased people more clearly than non-mediums. I also have never known someone personally that has seen one, and I have read that they are extremely rare. You have a better chance of winning the lottery, and you'd better lean towards winning the lottery ;)
However, I DO see clumped spirits, hundreds of them, sometimes on the news, sometimes in person, in photos, sometimes in readings. These are easier to communicate with, as they have shared energy and more "power". They look like nothing I've ever seen before, but I will try to describe it. When there are more than two, it is a nebulous and usually of brown/grey colour - but can range through the whole spectrum. They are like cotton-batting smoke that moves like stop-motion animation. They have many eyes, many mouths, etc, depending on what they're trying to get across. They're like living movie screens made of fluffy modelling clay.
One thing is for sure: when spirits get together and try to tell you something, you pay very close attention. If I am watching a movie at a theater and really enjoying myself and a spirit tells me that someone is in trouble, I will drop everything and call that person. They don't just tell you something bad is going to happen if that isn't the case.... well unless you're toying around with Ouija and find yourself chatting to a silly or mean-spirited ghost who's main goal in life is to freak you out or play pranks on you.
Maybe Mothmen are not spiritual convergences, but that is my theory. I have not met one, but if I ever do, I'll certainly post about it.