Entomopathogenic fungi, popularly known as zombie fungi, are life forms that infect and kill their hosts or seriously disable them in the process of completing their life cycle. They infect a variety of invertebrates like spiders, ants, moths, grasshoppers etc. They need the right temperature with a high level of humidity to thrive and sporulate. Their life cycle begins when spores are released from the predatory fungi. The spores land on a completely unaware host and start germinating into its body by gradually preparing for the reproductive stage. Preparation by the fungus might take days to weeks depending on the host and fungal species involved. During this stage, the fungus grows through the body of the host and gradually kills it. The fruiting body (mushroom) erupts from the host which again releases spores and the cycle of life continues.
We get to see many different species of these fungi all over the Western Ghats. The rainy season is the best time to spot them as the humidity levels are high, which helps them grow vigorously. Here are some photographs of dead hosts that I captured in and around the forests of Agumbe during monsoon.
Ants are one of the most commonly infected hosts. Some studies have concluded that once the spores start growing inside the body of the ant and the fungus is ready to reproduce, it hijacks and controls the brain of the ant completely, driving the ant out of its colony and makeing it climb high up on a plant or shrub around. It then bites into the plant and gradually dies. Driving the host higher will help the fungi to spread the spores effectively to the ants below. As seen in the picture above, the ant has bitten into the vein of the leaf & the fruiting body has emerged from the back of the neck.
Here we can clearly see the mandibles of the ant locked on to the major vein underneath the leaf.
Fruiting bodies grow from the ant’s head rupturing to release the spores of the fungus. The leg joints and antenna are covered by specialized cells that produce asexual spores that are transmitted by contact. Suspended by the long stalks (stroma), the round structures which are called ascoma (pink in colour) produce sexual spores that will be released onto the forest below, which lands on the other unsuspecting ants around and the lifecycle continues.
A dry corpse left behind by the fungus. Usually, little is left of the host’s body except for the exoskeleton.
Fungus sprouts from a winged ant. Going by the physical condition of the dead ant, it had probably died not too long before the photograph was shot.
Spiders are also commonly infected by entomopathogenic fungi. Seen here is a Neoscona sp. which would have been infected a couple of days before it was photographed. The fruiting body of the fungus has emerged out of the abdomen of the spider.
Another Neoscona sp. infected by the fungi with a different kind of fruiting body, growing throughout the body.
A lynx spider which is infected and completely taken-over by the fungus. The white layer covering the dead spider is called mycelium, which is the vegetative part of a fungus.
A crane fly with mycelium grown all over its body. These fungi get everything they need from the host’s body and use the moisture in the air to thrive and sporulate.
A white, snow-like fungus that has grown across the body of dead adult cicada, found just above ground level on a big tree.
A planthopper completely engulfed by the fungi, found under a leaf in a dense patch of the forest.
Fungi has grown through the body of the butterfly; the bottom part of the fungi has attached itself to the leaf and the fruiting body has grown all around the dead butterfly.
There are many species of entomopathogenic fungi across the world, and there is still a lot left to know about these interesting creatures. Lots of academic research projects attempt to understand the biochemistry behind host control by the fungus and there are also experiments being conducted worldwide to use these fungi as pest control agents in farming. Nature is full of interesting creatures and stories to explore.