The annual swarms of mayflies have made their way back into towns along the Mississippi River, and their presence is causing an uproar on social media -- at least for the folks who aren't used to this bug-filled phenomenon, anyway.

The annual "mayfly hatch" fills the air with blankets made of millions of mayflies, which acts like heavy fog -- only this one is worse, because it's winged-and-creepy-bug fog -- causing as much destruction as one would expect from clouds of winged insects taking over towns. So yeah, it's pretty bad at the moment.

That once-yearly hatching of the mayflies fills the air with bugs that leave the slimy, bug-covered surfaces on just about anything they come in contact with: streets, highways, cars, buildings and just about everything else.

The La Crosse, Wis. office of the National Weather Service says this year's mayfly hatch on the Mississippi River was so prolific that it created a bow echo on radar, similar to one that would be made by a significant rain storm.

And unfortunately for residents along parts of the Mississippi River, the blip isn't only made on the radar. Those massive swarms of flies? Well, they act like torrential downpours on the roadways, too -- giving about as much visibility to drivers as one would expect from millions of solid bugs swarming into roadways. So basically, none. Drivers are blinded by bugs.

According to reports, the mayfly hatch has been a problem up and down the Mississippi River. Police in Trenton, Wis., even say mayflies may have triggered a three-vehicle crash Sunday.

The road about 50 miles southeast of Minneapolis had become slick from the mayflies and their slime on Sunday evening, causing at least one of the drivers involved in the crash to lose control of her vehicle.

Visibility was limited at the time of the crash because to the massive cloud of mayflies in the air, police said, which may have added to the dangerous conditions.

Luckily for residents -- but perhaps not the flies themselves -- the mayflies die almost as quickly as they arrive. Within 24 hours, the flies will have lived out their slimy little lives and will go the way of natural order, dying in the streets of these small towns.

And what does that mean for residents? Well, millions of dead fly carcasses, of course. They pile up in roadways and on highways, and las year they had to be removed with a snowplow because the mass bug graves were so thick.

Pretty gross, no? Well, if you don't find that to be appalling, check these Twitter photos out. We dare you not to shudder.