A rare sight indeed when death springs life. Ants can be observed leaving their colony, ascending the nearest plant, clamping down on a leaf in what biologists call a ‘death grip’ only to wait to die, days later growths extend from the body of the deceased, growths very much alive and well.
The cause of this process is a parasitic fungus, a member of the genus Ophiocordyceps.
This fungus forces an ant to find a leaf in a location suited to fungal growth, a matter of precision. In some cases, all infected ants were found on leaves roughly 25cm from the ground, where temperature, humidity and leaf orientation are perfect for the fungus. This fungus can coordinate an ant’s behaviour with astonishing precision all while digesting the ant from the inside.
This highly complex interaction is not yet fully understood, we know the fungus never invades the brain however it is speculated that it could be controlling ants using hormones.
In social insect societies strong defensive measures are common, during social interactions infections can be detected and displays of aggression towards the infected noted, even removal from the nest. However, in the case of the parasitic fungus infected ants appear to continue moving through the nest undetected until leaving to die
The big question here, is does the pathogen change how infected ants interact with others or alter the chemical cues they emit which allow nest mates to detect the infection?
This hypothesis has been investigated, after observing 1,240hrs of footage researchers found no attacks towards infected indivduals and no significant difference in food sharing between infected and uninfected individuals. The key difference was the infected ants spent more time outside the nest, possibly an early signal of fungal manipulation. The significant finding from this research is that the coevolved parasite doesn’t seem to directly affect social dynamics within the colony.
The parasitic fungus is the cloaked assassin, the ant its pawn in the game of life.
How do parasitic fungi relate to pest control?
Not only do parasitic fungi play a vital role in maintaining sustainable insect numbers in the wild, they also hold potential as part of an integrated pest management system. As the fungi is not harmful to mammals the spores can be formulated into sprays, the key hurdle for advanced application and development within the pest control sector is the specific conditions required in temperature, humidity and light exposure. Parastic fungi has been applied with limited success, however with further study we may indeed see this fungi as a feature in mainstream pest management.