Fungal Infections on Insects
About Insects | Digging Deeper
While many understand that insects have predators themselves, rarely does fungi come to mind when pondering what attacks bugs.
Many insects can be effective predators of pests that damage or destroy plants and trees that people use. While many understand that insects have predators themselves, rarely does fungi come to mind when pondering what attacks bugs.
Birds, mammals, and even other insects prey upon and are parasites of all sorts of insects. In the more microscopic world of fungi, certain kinds don't necessarily feed on insects. Instead they make use of mobile insects to spread their spores and reproduce. The results for the infected insect is almost always suffering and death. One type of fungus makes 'zombies' of ants and ghosts of moths. This fungus is called Ophiocordyceps (formerly known as Cordyceps) and it has many species.
One species of this fungus is well-known in South America for its effect on ants. After crossing paths with the spores, an ant is unable to stop them from attaching to its body and growing into it. The infection impacts the ant's behavior, causing it to climb to a height in an area with ideal growing conditions for the fungus. The term 'zombie ant' comes from this takeover of the ant. Upon reaching such a place, the ant bites down on a twig or underside of a leaf, and a type of 'lock-jaw' sets in, preventing it from releasing the leaf. It eventually dies, and afterward, the fungus grows an antennae-like projection from the ant's head where it is more likely have wind spread its spores to a large area that can facilitate future infections and reproduction. The natural tendency for ants to travel in lines together means many individuals are infected at the same time, and large numbers of dead ants are often found very near each other in what entomologists call 'graveyards'.
Ophiocordyceps and other genera like it have been seen among in the U.S. The spores of one species is unwittingly eaten by a leaf-munching caterpillar. The fungus grows inside the caterpillar creates a shell around the body. The caterpillar desiccates into a mummy-like remnant of itself. Once dead, the fungus grows a stem-like projection from the head of the caterpillar that helps spread its spores into the air and on the ground around it, where subsequent caterpillars will eat them and share the same fate.
Infected moths become white or yellow, and grow long tentacles or antennae-like stems all over their diminishing bodies. They look familiar, but strange, like ghosts of their natural selves. The body of an infected moth may be found in the woods, where the spores are cast across the area making hosts of other moths.
This method of parasitism seems cruel, but it for the fungus, it is an advantageous way to make sure its species continues to survive. Encounters with an insect infected by it is uncommon, but we hope this helps explain what happened to that strange-looking insect.