Zombie Ants!

The Halloween season brings in hordes of scary creatures, from vampires to monsters to mummies. If we only look to the ant world, we can find all three. But these are not the scariest Halloween creatures to be found among the ants.

Ant Zombies!
In the tropical regions of the world, millions of ants are following the whims of an infection, possessed by a parasite that controls their brains for its own nefarious purposes. After maneuvering the ant into ideal position, this infection kills the vessel insect and explodes from its scull to give birth to more of its kind. Meet the Ophiocordyceps fungus and the ants it controls.


Photo Credit: David Hughes of Penn State / CC BY-NC 2.0


Ophiocordyceps. unilateralis is the villain in this horror story, a fungus that attacks ants and takes over their brains. Known as the “zombie fungus,” O. unilateralis attaches to the unsuspecting ant and breaks through its exoskeleton. The fungus spreads through the insect, producing chemicals that manipulate the ant’s behavior. The infected ant roams drunkenly, falling from high in the trees and erratically moving around on the forest floor, until the sun reaches its full height in the sky, at which point the ant ceases its wanderings. Under the influence of the zombie fungus, the ant chooses an ideal leaf. It bites down on the large vein of the leaf, and the ant’s jaw locks. The death grip is maintained until the ant dies and even after, as the fruiting body of the fungus explodes from the ant’s head, releasing its spores to infect more victims.

These unfortunate ants can be found in graveyards optimized for fungal growth (the correct temperature and humidity), and other ants actively avoid these sites, foraging in areas away from their dead peers.

Even movie makers are beginning to note the zombie ants. David Hughes, a leading expert in O. unilateralis, consulted for the movie World War Z and the videogame The Last of Us, lending real-world science to fictional zombies. The Last of Us imagines a mutated form of Ophiocordyceps that can infect humans, but we don’t have anything to fear from the zombie fungus anytime soon. The fungus has been specialized on ants for at least 48 million years, as fossil evidence shows. So humans don’t have to worry, but other bugs still need to keep their zombie defences high. There are strains of Cordyceps that infect many different arthropods, including tarantulas, grasshoppers and stick insects. The caterpillar specialist Ophiocordyceps sinensis is even used medicinally by humans. It is considered a “miracle cure” for many ailments and high quality specimens can sometimes sell for up to $50,000 dollars a pound!

So how do you stop a zombie infection? Ideas vary, but the zombie ant fungus has its own fungal foe. When O. unilatralis is infected by this hyperparasite, it cannot produce spores. This metafungus keeps the zombie number low and the spread of zombie-ism from progressing too fast through the ants.

In short, you don’t need to go to the movies to see zombies. Just go to the tropics and stay wary of fungi trying to control your mind (especially if you are an ant!).


Photo Credit: berniedup / CC BY-SA 2.0

Because That’s How You Get Ants: Flooding Causes Displaced Critters to Run for Shelter, Too

Most of you probably didn’t make it in to work today, and after my short drive to the Houston Museum of Natural Science this morning, I would say that was a good call. There were plenty of cars stalled in intersections, and I watched a sixteen-wheeler make a U-turn on 288 because the water level was too high under an overpass.  

Expensive car repairs aren’t the only reason to stay home during the flash floods we periodically experience. When the water rises, it carries with it everything that is buoyant.  This could be trash that was thrown out a car window, chemicals that spilled from a car during an accident or were poured down the drain, or the critters that live under the soil and in the bushes.


One of the most awesome and horrifying things you will hopefully never see during a flash flood is a raft of fire ants. These little guys instinctively know how to survive the catastrophic destruction of their home. They are light enough to float individually, but they stick together. This allows the ants at the base to hold up those above the water for a while. The roiling ball of ants turns constantly to allow every member of the ball to get a rest and to get enough oxygen. The ants at the edge are constantly looking for something dry on which they can cling. The instant they find a tree or a street sign, up everyone goes.

This is also horrific because sometimes that thing is you.


The ants, which are pretty upset at this point, will absolutely swarm you if you touch this little ball of hate. They will get to the highest point they can and then they will latch on.  With their piercing mouth parts. 

So, my friends. While I applaud an interest in the out-of-doors and making new friends, please wait until the city isn’t flooded to engage in both. Because sometimes you pick your friends…


…and sometimes they pick you!


Editor’s Note: Learn more about the behavior of ants and other insects at the Brown Hall of Entomology in the Cockrell Butterfly Center. (When the floodwaters recede, of course.)

ANTS! [Cockrell Butterfly Center]

I would say that my feelings about ants are very mixed at the moment.

Feasting time (close in) Kentridge Park
Creative Commons License photo credit: williamcho

As an Entomologist, I’m absolutely fascinated by ants. Who wouldn’t be fascinated by these tiny insects that form amazingly complex and efficient societies that parallel those of humans?

Millions of Ants

We often think of ourselves as the most intelligent or civilized but I think ants can give us a run for our money! Their ability to cooperate with each other, to build nests, care for their young, exploit and manipulate resources of all kinds and defend themselves in many different ways have made them so successful that we often butt heads. We are struggling to keep the upper hand in agricultural and urban situations. They can be quite a nuisance, but one can’t help being intrigued!

Ants share the order Hymenoptera with bees and wasps, some of which also live in social groups. Ant colonies can range from a few dozen to millions of individuals, but unlike bees and wasps, there is no such thing as a solitary ant. Many form permanent nests while others are nomadic. Most are predators or scavengers, while some grow their own food. Some even farm and “milk” other insects like we do with cattle.

The Queen

Ant colonies typically consist of a queen (occasionally many), the only member of the colony to reproduce, and her sterile daughters or workers. Each year, new reproductive females and males, called drones, are produced. The winged males and females leave the colony to mate and start new colonies. The males die immediately after mating and the females shed their wings and become queens of their own colonies. Some colonies do not even have queens, only reproductive workers called gamergates. Some ant queens can live for up to 30 years, placing them high among the longest lived insects.

If the queen is the heart of the colony, the workers are the blood. She produces them, they develop into adults and they take care of every aspect of the colony. Their responsibilities range from tending to the queen, the young, the nest and each other, to foraging for food or building materials and protecting the nest. The younger ants can be founding tending to the inner workings of the nest while the older ones, who are more expendable, have the more hazardous task of foraging.

Worker Ants

Workers can be different sizes, but the largest are the soldiers (remember, all are female!). Soldiers are strong, brave, and often have sizable mandibles! Any worker ant will sacrifice itself for the good of the colony. Who do you think invented suicide missions? This selfless devotion and ability to work together as one unified organism is what has made them so successful. There are so many ants that they make up an estimated 20% of the terrestrial biomass on earth. That number far surpasses that of vertebrates!

We have several types of ants here at the Cockrell Butterfly Center, some captive, and some, well, not so captive. A facility such as ours is a haven for pest species including cockroaches, fruit flies, and lots and lots of ants. We’ve always had ants in the conservatory. The conditions are favorable and the food, including fallen butterflies, is plentiful. In the conservatory, they are manageable and they don’t really bother anyone.

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Creative Commons License photo credit: emills1
Can you see the queen leafcutter ant?
She’s so much bigger than the rest!

Of over 12,000 described species of ants, only about 20 species are considered “pests” – i.e., they mess with humans or our possessions in some way.  The pest species are mostly very small ants including sugar ants, ghost ants, pavement ants, and others, that sometimes get into our houses and larders.  Unfortunately one of our uninvited residents is  perhaps the hardest species of household pest ants to control, crazy ants.

Crazy Ants!

Ant Fight
Creative Commons License photo credit: zayzayem

Crazy ants, also known as longhorn crazy ants (Paratrechina longichornis) have earned their common name from their erratic and “crazy” movements. They move extremely quickly and in all different directions. They do not form foraging trails like most other ants, instead, they will go straight towards a food source, then meander all over the place back to their nest, making their actual nest very difficult to find!

Crazy ants feed on a wide variety of things including live or dead insects, fruits, nectar, honeydew (a secretion from hemipteran insects), and many household foods. The best way to control these ants is exclusion, or  keeping them out and keeping food and water sources out of the area.

Crazy ants are very easily identified. They are small, dark colored ants with very long antennae. They are monomorphic, meaning all of the workers look the same and are the same size. They do not sting but they can be present in such great numbers that they can be quite a nuisance. We’re currently doing everything we can to combat them!

New Leaf Cutter Ant Colonies!

Luckily, there are also ants that we are glad to have. After losing our tropical leaf cutter ant colonies in 2010, we have been blessed with 3 new colonies of Texas Leaf cutter ants (Atta texana).

I bet you didn’t know that leaf cutter ants are native to Texas! Leaf cutter ants are very fascinating and fun to watch! The workers use their powerful jaws to cut pieces of about 200 different types of leaves. They do not eat the leaves but carry them back to the nest. Once there, they chew them into a mulch that they use to grow a special type of fungus. The fungus is what the ant larvae feed on, so they are true fungus farmers!

Leaf cutter workers are polymorphic, meaning the workers differ in size and appearance. The smallest workers, called minims, are meant to tend to the fungus garden, queen, and brood. The minor workers, which are a bit bigger, patrol the nest and are the first line of defense. Mediae are larger workers with strong mandibles that forage, cut leaves and bring them back to the nest. The largest are the major workers. They act as the soldiers and are often very large with big strong mandibles that can break the skin. I know this from experience!

Leaf cutter ants also do not posses a stinger, but they sure do bite and will not let go! The mutualistic relationship between the ants and the fungus is quite incredible. The fungus must be actively maintained and cultivated by the ants. It constantly needs new fresh leaves to grow and survive. The ant larvae feed exclusively on the fungus and need it in order for them and the colony to survive. The ants constantly monitor the fungus to see if any leaves are toxic or if any other competing fungus is growing. They will destroy any other fungi with a bacterium that grows on their skin and secretes antimicrobial chemicals. WOW!

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Creative Commons License photo credit: emills1
A Mediae worker going after a leaf

Two of our new colonies came from the University of Texas, which was so generous to donate them to us! When we got them I noticed that the fungus gardens, which are usually green, were all white. These ants had been fed on oats instead of leaves, which they can apparently manipulate in the same manner. It’s really cool, they look like some formations you would find in a cave. One of these colonies will soon be on display for everyone to watch as they busily carry leaf fragments to their gardens.

There are so many interesting things about ants. They really are diverse and fascinating. I encourage you to read up on them a little bit; even just by clicking the links in this blog, you may find out things you would have never expected!

Next time you see ants trailing in your house or outdoors, don’t think of them as just a nuisance, think of how incredible they are and how hard they work. You may have a newfound respect for the little critters.

Until next time, happy bug watching!

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Creative Commons License photo credit: emills1
The white fungus garden

Adventures Among Ants

Ants are endlessly fascinating.  They seem so HUMAN in the way they bustle around, cooperating in all things whether building great metropolises, hauling food, overcoming enemies or taking care of their queen and their baby sisters.  They epitomize industry and selfless devotion to the cause – their colony.  Of course as children we may have squished dozens of these little workers, but we have also watched their activities in wonder, marveling to see so many of our own behaviors reflected in their activities.

Dagger-Jawed Army Ants
©Mark W. Moffett/Minden

With 12,000 species world-wide, ants are the most diverse and widespread of the social insects, which include termites and some wasps and bees.  Ants are found on every continent and in every habitat, but are especially successful in the tropics.  Everywhere they are abundant and in many habitats are the dominant organisms, in terms of individuals far outnumbering all other animals.  They have few enemies and many have long-lasting, stable colonies.  Individual ants are remarkably long-lived, as insects go, with queens living as long as 13 to 15 years or so, and some workers surviving 4-7 years.  Unlike other social insects such as termites or honeybees, which are quite specialized, ants have many different ways of life.  Some have mutually beneficial relationships with plants or other insects.  Although a few ants are household pests, and some may cause agricultural or other damage, many are beneficial in terms of controlling pest populations, cleaning up wastes, and aerating the soil.

All ants are social; there are no solitary species.  Some are tiny, less than 1/16 of an inch long, while some tropical species are over an inch in length.  Depending on the species, ant colonies may be made up of only a few individuals, while others number in the millions.  In this and other ways, ant societies appear to parallel human societies.  Some are simple hunter-gatherers, with little specialization among workers, while others have huge and sophisticated societies with highly specialized tasks divided among different “castes.”  Driver ants in Africa and army ants in South America are ruthless predators, moving in huge numbers from temporary bivouac to bivouac in search of prey.  Any of us who read “Leinigin versus the ants” when we were in school can still remember the terror inspired by the image of a huge river of driver ants overrunning everything in its path.  Leafcutter ants also have huge colonies, but theirs are sedentary and underground, sometimes lasting more than 20 years.  Leafcutters are farmers, chewing up fresh leaves and fertilizing them with their saliva and feces to provide a rich substrate for the fungus they cultivate as food for the colony.  Harvester ants in dry grasslands stockpile seeds in underground storage areas.  Other ants are ranchers, herding and protecting groups of tiny, honey-dew producing insects such as scale and aphids.  Desert-dwelling honeypot ants use their own sisters as “cisterns” to store honeydew.  Formica ants in boreal forests make huge mounds of pine and spruce needles, which serve to regulate temperature and humidity.  Some ants do no work themselves, instead robbing pupae from neighboring ant nests, and then forcing the captured ants to work as slaves.

Dr. Mark Moffett
Photo by Frank J. Sulloway

Mark Moffett, renowned National Geographic photographer and explorer, has made a career out of his fascination with ants, and will be at the museum to talk about his favorite organisms on Wednesday, September 15.  An enthusiastic speaker with – needless to say – wonderful photographs – Mark will regale his audience with tales of warfare, industry, and cooperation.  He encourages all ages to attend!

Don’t miss Mark’s distinguished lecture at HMNS:
Adventures Among Ants: A Global Safari with a Cast of Trillions
Mark Moffett, Ph.D.
Wednesday, September 15, 6:30 p.m.

Purchase your tickets in advance here.

Check out Moffett on Colbert in May 2010: