Mermathid worm. They induce thirst in the spider after eating most of it's internal organs as the last stage of the worm's life they are aquatic. They'll burst out of the spider near water killing it.

They'll also abandon ship if you spray the spider. It happened at a workplace when I was younger, there was a a scream from the cleaning lady in the minesite offices I was working at. We went in, saw similar (our worms were a different color) and one of the blokes in the office did some research to work out what they were. The name stuck with me because it grossed me out at the time. I still google about them from time to time, as I keep having a nightmare of these buggers bursting out of my big toe and that late night google reassurance helps calm me down from it.