Every evening, the ant would leave the colony and climb to the top of a blade of grass. Then, the ant would pierce the top of the grass with its strong jaws and wait there. At dawn, it would return to the colony and continue to perform its daily routine. Yet, night after night, the same ritual would be repeated until one evening, a passing sheep ate the blade with the ant on it and, inadvertently, gave a successful conclusion to the complex process behind this apparently unremarkable scenario.
One obvious question to ask would be: what benefit could possibly accrue to the ant from a behavior that caused its death? However, the question that can point us in the right direction to solve the mystery is “Cui bono”. In other words, “who benefits?” On closer examination, the real beneficiary is a parasite called “Lancet fluke” (Dicrocoelium dendriticum) which needs to reach the intestines of grazing mammals in order to reproduce. A group of them will start their lives in the digestive tract of a snail and after being excreted, will invade the body of an ant. At that point, one of them will take control of the ant’s nerve cells. That will enable them to direct the ant every evening to the top of a blade of grass until a sheep eats both the ant and the grass. Afterwards, the parasites will live their adult lives inside the sheep and reproduce. When the new parasites (in a larval state) are excreted by the sheep, a passing snail will give a new beginning to the reproductive cycle. Continue reading