An image of a creepy-crawly posted in the subreddit Oddly Terrifying has gone viral on Reddit over the last few days. 

The beasty in question is a house centipede (Scutigera coleoptrata), found in an apartment in Japan. 

One of the reasons why many people are freaked out by the critter is the vaguely threatening claim that "they are fast" – which is entirely true. Despite having to coordinate up to 15 pairs of legs, the centipedes can run at speeds up to 40 centimeters (16 inches) per second.

Ok, to be fair that's about 0.9 miles per hour (1.45 kilometers per hour) which is pathetic compared to us mighty humans – but when you see an insect move at that speed, and up walls and ceilings, well, take a look for yourself.

 

As one user puts it, it can run "from your forearm to the back of your sinus cavity in 2 seconds". The good news is, they are unlikely to cause you any harm (there is bad news later on, we promise). 

Gejigeji, as they are known in Japan, are actually something you probably want in your house. The insectivores will eat up any other insects in your house, as well as arachnids. They'll gladly munch on cockroaches, termites, bed bugs, silverfish, spiders and any other critters you'd rather be rid of. They are venomous, delivering stings with their front legs, but it's something that they very rarely do to humans, and if they do you probably won't experience anything other than mild discomfort.

"If you see them, you have something else infesting your home that's worth eating, but you don't notice them because the house centipede is actively taking control of that problem for you," one Reddit user wrote.

"Now, if you have a TON of house centipedes and they are often sighted.. You should actually be worrying less about them, and more about what horrible thing is in your house to attract so many..."

"Goodnight! Sleep well!"

Right, now onto the bad news: there are species of centipede out there that are a bit more nightmarish, specifically the Mukade (Scolopendra subspinipes).

These centipedes can grow up to 38 centimeters (15 inches), and deliver a lot more painful sting that sometimes requires treatment, or at least anti-inflammatories. One death has been associated with the sting of the centipedes, a 21-year-old who was stung three times by the creatures over a period of nine months. Her doctors believe that her death was the result of an allergic reaction upon a fourth sting, caused by the prior stings.