Fungi and insects are two of the oldest living groups that appeared on earth approximately 400 million years ago. This was long-before dinosaurs, birds, and mammals. Insects such as the giant dragonfly were masters of the sky and fungi was master of the land.
Through evolution, insects and fungi developed important cooperative relationships, also called symbiosis. Symbiotic associations are abundant in nature, showing us that “two are better than one.” Lichens and mycorrhizae are two examples of symbiosis between fungi and photosynthetic organisms.
Fast Fact:Lichens are not a single organism, but rather the result of a partnership between a fungus and typically a green alga or a blue-green cyanobacteria. Mycorrhizae represent a symbiotic relationship between plant roots and a fungus.
The interaction between fungi and insects is another example of how symbiosis can be beneficial to both organisms. When we hear of fungi-insect symbiosis we might think of the relationship only as a parasitic one where the fungi attack and usually kill the insect. However, this is not the only type of relation these organisms have established. Entomologists, who study insects, have found that about 4,000 species of insects cultivate fungi as their primary source of food. In return, fungi have their spores dispersed by the insects. This sounds like a fair deal to me!
Insects that cultivate fungi, or so called fungivorous insects, have developed adaptations that allow them to exploit this abundant resource. For example, the winged female ant of the genus Atta, carries spores in a small pocket in her mouth. When a suitable nest is found, she starts growing fungi and, she begins laying eggs once the fungal colony is established. Similarly, the wood-dweller beetles of the genus Xyleborus, carry the fungal spores in special structures and leave the spores inside the trees when they invade them. This video shows the close symbiotic relationship between leaf cutter ants and fungus.
Fast Fact: There are only three groups of insects that are known to cultivate fungi for food: ants, termites, and beetles.
Just as humans do in the fields, fungivorous insects need to work hard to ensure their fungal gardens are clean and free of pathogens and pests. They regularly weed and monitor their fungal crops. It has even been found that some species use antibiotic treatments against fungal parasites. These insects have learned to select, maintain, and propagate their crops—a skill that we thought only humans possessed.
Science Daily: Ants Are Experienced Fungus Farmers
Caldera EJ, et al., “Insect Symbioses: A Case Study of Past, Present, and Future Fungus-growing Ant Research”, Environ. Entomol. 2009, 38(1): 78-92.
Iyer G. 2011. Fungus farmers. Frontline, 28:24. http://www.frontlineonnet.com/fl2824/stories/20111202282406400.htm
Mueller UG, et al., “The Evolution of Agriculture in Insects”, Annu. Rev. Ecol. Evol. Syst. 2005, 36, 563-595.
Article first published May 10, 2012