Brainwashed by a parasite

The ants in these photographs have fallen victim to parasitic fungi which manipulate the behaviour of their host in order to increase their own chances of reproducing.

The spores of the fungus attach themselves to the external surface of the ant, where they germinate. They then enter the ant’s body through the tracheae (the tubes through which insects breathe), via holes in the exoskeleton called spiracles. Fine fungal filaments called mycelia then start to grow inside the ant’s body cavity, absorbing the host’s soft tissues but avoiding its vital organs.


Carpenter ant (genus Camponatus) infected with a parasitic Cordyceps fungus. Gilbert Lab, University of Texas, Austin.

When the fungus is ready to sporulate, the mycelia grow into the ant’s brain. The fungus then produces chemicals which act on the host’s brain and alter its perception of pheromones. This causes the ant to climb a plant and, upon reaching the top, to clamp its mandibles around a leaf or leaf stem, thus securing it firmly to what will be its final resting place.

The fungus then devours the ant’s brain, killing the host. The fruiting bodies of the fungus sprout from the ant’s head, through gaps in the joints of the exoskeleton. Once mature, the fruiting bodies burst, releasing clusters of capsules into the air. These in turn explode on their descent, spreading airborne spores over the surrounding area. These spores then infect other ants, completing the life cycle of the fungus. Depending on the type of fungus and the number of infecting spores, death of an infected insect takes between 4-10 days.

The carpenter ant in the photograph on the right has been infected by Cordyceps unilateralis, which is but one of thousands of species of entomopathogenic fungi, more than 400 of which belong to the Cordyceps genus. Between them, these parasitic fungi infect at least nine different orders of arthropods, including the Odonata (dragonflies and damselflies), Blattaria (cockroaches), Hemiptera (aphids, cicadas and leafhoppers), Coleoptera(beetles), Phasmida (stick insects), Hymenoptera (ants, bees and wasps), and Lepidoptera (butterflies and moths). The host range of an individual species is, however, restricted to one species or to a small number of closely related species.

Because they are considered as environmentally safe, natural mortality agents, entomopathogenic fungi are used as biological pesticides to control pest species. For example, Metarhizium anisopliae was first used over 100 years ago to try and control the wheat grain beetle Anisoplia austriaca. More recently, researchers have investigated the use of Metarhizium anisopliae, a species which infects the African mosquito Anopheles gambiae, to control the spread of malaria.

Entomopathogenic fungi are not the only parasites that can modify the behaviour of their hosts. Equally remarkable is the nematomorph hairworm Spinochordodes tellinii, which is also known as the horsehair worm or the gordian worm, because of its resemblance to the knot created by the Phrygian king Gorius. (According to myth, Gordius used his knot to tie a chariot to a pole, and declared that whoever could untie it would rule all of Asia.)

The juvenile gordian worm parasitizes land-living arthropods such as grasshopers, locusts and beetles, but the adult is a free-living aquatic species which can only reproduce in water. Inside the host, the microscopic larvae feed on surrounding tissue, and develop into long worms which can reach up to 4 times the length of the host, and which remain within the body cavity of the host as a long, coiled mass. After metamorphosing, the adult worm induces its host to leave its terrestrial habitat, and to commit suicide by jumping into water and drowning itself, so that the worm can emerge.


Spatafora Lab, Oregon State University.

David Biron and his colleagues have used proteomics to characterise the proteins synthesized by the gordian worm in order to determine how it manipulates its host’s behaviour. They have established that the worm synthesizes proteins which mimic those produced by the insect. These include proteins of the Wnt family, which are involved in the development of the nervous system, as well as others which interfere with the neurotransmitter systems involved in the host’s geotactic behaviour (its oriented movements in relation to the Earth’s magnetic field).

Because the genes encoding these proteins are contained in the worm’s genome, but have a direct effect on the insect’s central nervous system when they are expressed, the relationship between the gordian worm and its host is an example of what Richard Dawkins called the extended phenotype, whereby genes expressed by one organism have an effect on the appearance or behaviour of another. (Entomopathogenic fungi and their hosts are also an example of an extended phenotype.)

Incredibly, the gordian worm can survive predation on its host. Parasites use various strategies to survive host predation. For example, some develop quickly, in order to emerge from the host before it is preyed upon. Grasshoppers and crickets are preyed upon by fish and frogs; the gordian worm can escape this predation by wriggling out of the mouth, nose or gills of the predator once it has emerged from a host that has been eaten.


Biron, D. G., et al (2005). Behavioural manipulation in a grasshopper harboring hairworm: a proteomics approach. Proc. R. Soc. B. 272: 2117-2126. [Full text]

Thomas, F., et al (2003). Biochemical and histological changes in the brain of the cricket Nemobius sylvestris infected by the manipulative parasite Paragordius tricuspidatus (Nematomorpha). Int. J. Parasitol. 33: 435-443. [Full text]


67 thoughts on “Brainwashed by a parasite

  1. Human beings have something similar to the first example. It enters through the ears at an early age, germinates in the mind, and causes the host to destroy rival communities, whilst reproducing abnormally rapidly, thus permitting the parasite to breed, exit via the mouth, and infect others. It is commonly known as..

  2. Cordyceps fungi were recently featured in the BBC’s Planet Earth series, including a truly creepy time-lapse sequence of a fruiting body erupting from an ant’s head.

  3. I too saw the programme and it has given me some fantastic ideas for stories…perhaps verging a bit too close to X-Files…nonetheless the image of the ant in time-lapse death sequence was truly a great example of how creepy and “alien” nature can be.

    Imagine a human version! Eeeeeep!

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  7. phenomenal insights of the small worlds…
    for more mindcontrol parasites (this time: snails) check this mindblowing film out:

    have a nice mindcontrolled day;) fu

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  9. This idea was used 10 years ago by a Japanese author for a comic book. A villian had the power to infect anyone who fell onto lower ground than him with spores and fungus. Jojo’s Bizarre Adventure Stand Name: Green Day.

  10. Hi,
    I am writing a review on host manipulation by parasites. Where can I find information (a scientific article) regarding the following quote in the blog “The fungus then produces chemicals which act on the host’s brain and alter its perception of pheromones. This causes the ant to climb a plant and, upon reaching the top, to clamp its mandibles around a leaf or leaf stem, thus securing it firmly to what will be its final resting place”
    Thank you for your kind help,

  11. Libersat, I found that information on a website when I googleed “Cordyceps”. I can’t remember the site unfirtunately, but the papers I’ve linked to in the post contain information about how the chemicals produced by the horsehair worm affect the brain of of the host. I hope this is of help to you.

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  14. Hey there was surfing through the internet and found your page on google . Enjoyed the good read wanted to say Happy New Year and keep up the good work.

  15. Can you tell me your reference for this info: “The fungus then produces chemicals which act on the host’s brain and alter its perception of pheromones”

    I’m working on a project (I’m a freelance writer) about this and finding someone who works on bullet ants OR Cordyeps as been impossible… I need to verify that info that you’ve posted. Thanks!

  16. Wendee, please read the reply to Libersat’s comment above. I had the same difficulty finding scientific information about this fascinating topic. Click on the pics and you’ll be redirected to the websites of labs doing research into manipulative parasites.

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  19. While Nature finds unusual solutions – I hope that this form of parasitism doesn’t inform some of the boffins at DARPA!! Though I can see some applications in the business world, a Harvard Business Review article ticking away…

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  22. Don’t wish to disturb anyone too much but there are a number of parasites that effect humans causing behavioural changes, for example Toxoplasmosis (which comes from cats):

    Changes to behaviour include; increased risk taking, slower reactions, feelings of insecurity and self-doubt, kitten-like behaviour in women (!), and more aggressive behaviour in men.

    Strange indeed, at least it doesn’t grow sprout forth from ones brain!

  23. In the 30s Clark Ashton Smith wrote a story about this called “The Seed in the Sepluchure” Parasitic plant grows from jungle explorer’s skull. Wonder if he had heard of the fungus?

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  26. We just found a tomato worm in our garden littered with parastic fungus growing from it’s back. It was even sprouting a few leaves as well. I got some pictures of it. I remember seeing this from Planet Earth. We actually still had the episode in our DVR, and just re-watched it. Should we be concerned about finding this in our garden???

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  28. After seeing this on television, I immediately e-mailed the CDC because I believe that Morgellan’s Disease is in fact, a parasitic fungus. It seems so elementary to me now. I wonder if anyone is following up on this? Jennifer

  29. Mother of God!!!! Those were horrifying and amazing videos. Thank you for giving me that glimpse into a seldom seen world. I have always been facinated by parasites of insects.

    To Quote Startrek – The Doomsday Machine
    “They say there’s no devil Jim…but I’ve seen him. Straight out of hell he came” – Commodore Decker

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  31. cordyceps fungus it used in china for hundreds of years to cure many ailments of the body a recent product lanched here in america using cordyceps fungus is MAXGXL interesting that the same fungus kills the insect host and cures the human

  32. Research should investigate human infections. The same cataclysm that destroyed the dinasours perhaps so reduced the environments sustainance that the ‘serpent’ has receeded to smaller perportions in order to survive. What we now call mental illness was once called demon possesion simply because there lack of med science reality. Biblical writers didnt have the word emotion, so they used the word spirit. There is no coorespondance between predator size and ability to kill. Organizations have members and Organs have membranes both of which define its boundries. Science and religion cannot be seperated and who thinks they can really misunderstands both. A religion without connection to physical natural science and reality is simply a wheel spinning without touching the ground. Useless.

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  37. I believe i have been fighting morgellan’s disease for several years. I am making progress.
    It is hard. I have found some things by experimentation that are taking me in the right direction. I would like to learn if anyone else has found some things that work. It is parasitic. Everything I do confirms that to me. Thank you.

  38. Trying to understand Morgellons is what brought me to this site. Morgellons is a scary disease. The YouTube clips are just as freaky as the clips above. Mostly because it is affecting tens of thousands of humans and researchers don’t have a clue what it is, how it is contracted/spread, or how to combat it. It SEEMS to be a parasitic fungus type infection, yet researchers have found its composition to be neither. My mom has had success using colloidal silver and recently she has been doing regular treatments in a foot ionizer. She has cleared a LOT of “gunk” from her body out the bottom of her feet. Others have also had great success by drastically changing their eating. The guy who started the Canadian Society for Morgellons has strong advice on proper diet. He has cured himself (his number is on the web site Hope this helps.

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  41. It makes e wonder if there is a link between the brain control of the cordyceps fungi and the halucigenic affects of Philysobe magic mushrooms. Fungi can do some pretty crazy things! We still dont really know what causes us to halucinate from Phiysobe mushrooms, nor lsd to add to that. Again, although lsd is a chemical it is derived from wheat rhye fungi – creepy hey?!

  42. The hallucinogenic effects of mushrooms and lsd are due to the ability of their indole based structures to pass through the blood-brain barrier due to their very close physical resemblance to our own inherent biochemicals like seratonin, melatonin, etc…

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  47. A human version? It already exists, but it is a work of fiction, so no need to be afraid. It of course comes from our favorite Horror Survival series…


    The fourth installment.

  48. Planet Earth Jungles. I just watched it with my daughter who is 5, she loves all Planet Earth Movies. I am fascinated by this population control fungus.

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  54. oh snap. So I too just recently watched the Planet Earth episode with Cordyceps fungus, and it made me want to write a sci fi about a human version. I’m now aware there are similar things and many onther sci fi things that are OBVIOUSLY a take on this kind of thing, but I’m trying to make mine as realistic as possible… so what other things should I look into? and human things that could develop into this kind of thing? is there any mutation that could occur in the far future in a fungus that enables it to infect mammals? ANY HELP APPRICIATED THANKS!!

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