Shades of Scott Westerfeld's brilliant vampirism-as-parasitic-infection novel Peeps — New Scientist reports that a worm that thrives in grasshoppers and crickets somehow convinces its hosts into drowning themselves, leaving the worms in a better breeding position:
The parasitic Nematomorph hairworm (Spinochordodes tellinii) develops inside land-dwelling grasshoppers and crickets until the time comes for the worm to transform into an aquatic adult. Somehow mature hairworms brainwash their hosts into behaving in way they never usually would – causing them to seek out and plunge into water.
Once in the water the mature hairworms – which are three to four times longer that their hosts when extended – emerge and swim away to find a mate, leaving their host dead or dying in the water. David Biron, one of the study team at IRD in Montpellier, France, notes that other parasites can also manipulate their hosts' behaviour: "'Enslaver' fungi make their insect hosts die perched in a position that favours the dispersal of spores by the wind, for example."
(Thanks, Nick!)
