I did research on these things when I was researching the "Dad" series on YT
I will use the Ophiocordyceps Unilateralis parasite as an example. The Ophiocordyceps Unilateralis (Or as I call it, the zombie virus) is a fungus that infects an ant near it. While the fungus is in the ant, it will slowly control it's bodies so it has no will over it, and hijack it's mind. Once completed, it basically has full control of it's host after a certain period of time, and making the ant die later. Before death, however, it will produce another fungus from the ant, infecting the next insect.