Fear of spiders is quite common, and our eight-legged friends often get a bad break. If you see one in your house, it’s hard to rationalize in that moment that it’s probably only there because your house also has lots of other things for it to eat. Without even thinking, it’s easy to reach for a shoe (or something else that you don’t mind being covered in guts) and smash it, or reach for a pesticide spray (or furniture polish or Lysol, depending on what’s handy) and drench it with half the can until it stops kicking.

Presumably, the soul-biting panic will subside as soon as the spider is dead, but what if things actually got worse afterward? After Brent Askwith sprayed a spider in his house in Australia, a long, brown worm unexpectedly crawled out of the spider’s corpse. He recorded the worm and uploaded it onto YouTube with the very accurate title: “WTF IS THIS?!?”

Let’s take a look at the worm, before we answer Askwith’s question about WTF it actually is:

Since the video’s release, there has been some debate over the identity of the worm. While many assume it is a Gordian worm, also known as a horsehair worm, it is more likely a member of the family Mermithidae. Though both types of worms are endoparasites and look incredibly similar, Mermithids have a larger documented history of infecting spiders, while Gordian worms are more commonly found attacking organisms like beetles, cockroaches, and crickets.

Mermithidae reproduce in the water and the eggs are often ingested by insects. When the worm hatches, it begins to eat and eventually goes dormant. When the primary host is ingested by a spider, the worm becomes active again and can grow up to 10 cm long. 

While we know Askwith used quite a bit of pesticide to kill the spider (note the liquid and the foam in the video), it’s not entirely clear how much napalm he used on his house after the worm emerged.

Note: Use of pesticides is not recommended by most entomologists. However, in this instance, it was likely doing the spider a favor. 

Want more parasites? Don’t forget to check out videos on a praying mantis, caterpillar, and an ant as they succumb to their respective body invaders.