On a recent trip to Belize, insect researcher Mark Moffet was infected with a parasitic botfly. Moffet allowed the botfly to gestate in his hand and later filmed its birth. NSFW because throwing up on your computer is poor form.
[...A] parasitic larva called a botfly entering his hand during an expedition to Belize. The maggot took ten weeks to grow to "maturity," surviving Mark's subsequent trips to Honduras, Botswana, and Zimbabwe. It finally emerged on 2 December 2010, at the end of a meeting with the environmentalist E.O. Wilson at Harvard.
True story: I was drinking a banana smoothie when I first saw this and was instantaneously green around the gills. This video is a great way to permanently alienate everyone you know.
For more of this, check out Moffet's book Adventures Among Ants.