A parasite infects your body, eventually chowing everything that isn't necessary to keep you alive. At the end, it takes control of your mind, forcing you, a non-swimmer, to commit suicide by jumping into water so it can emerge to live and breed in fresh water.
To humans, the scenario sounds like a decent plot for a Hollywood horror film. To land-dwelling grasshoppers and crickets, it's the real world.
An article in New Scientist details how the parasitic Nematomorph hairworm (spinochordodes tellinii) develops inside land-dwelling grasshoppers and crickets until it's ready to transform into an aquatic adult. Researchers at the French National Center for Scientific Research in Montpellier, France, led by Frédéric Thomas and David Biron, have shown the worm brainwashes the grasshopper by producing certain molecules that mimic the host's own proteins to control its behavior.
That parasites can influence their hosts' behavior to its benefit is well known. The rabies virus, for instance, drives rabid animals to bite others to transmit the virus.
What isn't known exactly is how the hairworm manages to infect a terrestrial species. A New York Times article says researchers suspect the larvae, minuscule on hatching, first infect aquatic insects like mosquito larvae, hiding as cysts in their tissues. When the adult mosquito flies away and dies, it may be eaten by a grasshopper or cricket.
The hairworm then develops, “eating absolutely everything not essential to keep its host alive,” the article quotes Thomas as saying.