The fruiting body of a fungi growing out of the ant's head

We usually think of a ‘zombie’ as something that has had its body taken over and is no longer in control of their movements or behavior.  Although this is usually something of horror films, there is a real life example being found around the world.  It is an example of parasitism, and in this case the parasite is a fungus and the host is an ant.

Fungi have some obstacles to overcome when it comes to reproduction.  Often times they will use wind or water to help spread their spores to new areas, but what if you live on the floor of a dense forest, where travel by either wind or water don’t work very well?  A few species of fungi have found a means of transportation in the ants that continually walk around the forest in the search for food.

The first species of fungus, Ophiocordyceps unilateralis, that takes over an ant’s body was discovered in 1865.  These types of fungi exist all over the world, and four new species have recently been discovered.  These fungi first infect an ant when an ant walks by and picks up some of the spores.  The ant goes about its regular activities for a few days, but then the fungi takes over and the ant is now a ‘zombie ant’.  Once this happens, the ant can no longer follow the regular trails the other ants use to travel to the colony, but it walks haphazardly in zig zag lines and often suffers from convulsions.

The convulsions are all part of the fungi’s plan.  The ant eventually falls from its home in the canopy of the tree to the forest floor, which is a much better environment for the fungi to spread its spores because it’s cooler and has more moisture.  Once on the forest floor, the ant crawls to a leaf about 9-10 inches above the soil and takes its final ‘death grip’.  To take the death grip, the ant clamps its jaws onto one of the larger veins on the bottom of a leaf and never lets go.  The ant can’t let go.  The fungus causes the muscles in its jaw to deteriorate and detach so that the ant can no longer open its jaws.

Eventually the ant dies while remaining clamped onto the leaf, and the fungus completes its task of releasing the spores.  The sprouting body of the fungi grows up out of the top of the ant’s head and the spores fall to the forest floor, lying in wait for another ant to walk by and unknowingly become another ‘zombie ant’ to repeat the life cycle of the fungi. 

Scientists hope to continue research into these unique fungi in the hopes of developing biological insecticides that could control the populations of specific insect pests.  This could also lead to more studies of how organisms have evolved to control the behavior of other organisms in different kingdoms.

What could be some issues with using parasitic fungi to control insect populations?  How else could research into these parasitic relationships be beneficial for us?  What are other examples of parasites taking over their host completely, including mind and body?