How a parasitic fungus turns ants into zombies can be explained by looking at the reproductive behavior of this particular fungus. The name for the fungus in nature is Microsporum and it normally occurs on plants as either a fungus or mold. As an organism, the fungus is a single-celled organism and it cannot reproduce by division. It must reproduce by means of division and that is what happens when it infects its host cells. The disease causing Microsporum fungus takes over the living tissue present in the case of the infected animal or human.
There are many species of fungi that cause infection and they usually occur naturally on plants. If you have ever noticed spots of mold growing around your house or on your garage floor, you probably are dealing with one of these natural species. Most of the time you will not even know that you have been infected with any kind of fungal infection until you notice that the ants are dying. When you look closer, you will see that the fungal infection has made the infected areas really ugly and they look like they are ready to collapse.