Source

Parasitic Castration

Jade, one of our resident arachnophiles, forwarded this lovely set of photos. You're looking at what happens when a Mermithid (almost a pretty word) worm (not a pretty word) reaches maturity.

Here's a quote from the post on What's That Bug:

Mermithid worms are internal parasites whose infective larvae enter spiders directly or via ingested food. Once inside the spider, the tiny worm obtains nourishment from it's hosts body fluids, digestive glands, gonads ('parasitic castration') and muscles...Eventually in a scene reminiscent of the movie "Alien", the gorged worm bursts out of the body of the debilitated spider, which finally dies after this macabre event...

This worm, like others I've posted on, often directs its host to seek water in its final moments of life.