How Termites Work


In a lot of ways, termites are a paradox. They're strong enough to eat a house, but their bodies are soft, delicate and prone to drying out. Soldiers, whose sole job is to defend the colony, can't even feed themselves. Adult termites develop wings so they can leave the colony and find a new home, helping the termite population grow. But winged termites are terrible flyers, and most don't survive the journey.

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At the same time, termites are survivors. They've existed for about 50 million years, and today there are close to 3,000 termite species living in most temperate parts of the world. In Africa and Australia, termites build enormous mounds that can last longer than the colony itself can survive. There are plenty of methods for discouraging termites from feasting on a person's home, but many species have a knack for finding ways around them. Once a colony moves in, it can be difficult to exterminate.

Lots of factors combine to allow termites to do all this. First, like many types of bees, termites are social. They cooperate to find food, raise young and build and defend nests. Second, they compensate for their weaknesses -- they keep their nests moist so their bodies don't dry out, and they build shelters to protect themselves from predators and the elements. Third, they do big things in small steps. They take tiny bites of wood to use as food, and they carry tiny particles of dirt and waste to build their homes. They also get help from even smaller organisms, like fungi, bacteria and protozoa.

In this article, we'll answer the most common questions about termites. How do they build such enormous mounds, and what do these mounds look like on the inside? How can homeowners keep termites away from their property or tell if there's an infestation taking over the woodwork? How can people tell the difference between swarming termites and flying ants? We'll begin by taking a look at how termites are able to eat and digest a substance people think of as inedible -- wood.

Termite Anatomy

Termites are insects. They're most common in tropical environments, although they can live just about anywhere as long as the ground doesn't completely freeze in the winter. Although many people think termites resemble ants, they're more closely related to cockroaches.

All termite species are social, and termite colonies are divided into groups, or castes. Members of each caste have different jobs and different physical features:

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  • Reproductives lay eggs. Most colonies have one pair of primary reproductives -- the king and queen. In some species, secondary and tertiary reproductives assist with the egg-laying. Only the king and queen have eyes. The rest of the termites are blind and navigate using scent and moisture trails. Kings and queens are usually darker than the rest of the termites in the colony.
  • Soldiers defend the nest from invaders, typically ants and termites from other colonies. In most species, soldiers have large heads and strong, pincer-like mandibles. Soldiers' heads are often darker than their bodies. Some species can secrete a toxic or sticky substance from their heads, which they use to kill or subdue intruders.
  • Workers are a milky or creamy color. They have smaller, saw-toothed mandibles, which allow them to take small bites of wood and carry building materials. As their name suggests, they do most of the work in the colony. They dig tunnels, gather food and care for young. They also feed the king, queen and soldiers, who are unable to feed themselves. Workers and soldiers are sterile.

Termites' food comes from cellulose. Cellulose is a polymer, or a compound made of lots of identical molecules. It's a tough, resilient compound found in plants. Cellulose is what gives trees and shrubs their structure. The molecules that make up cellulose are glucose molecules -- as many as 3,000 of them. In other words, cellulose is made of sugar.

However, unlike the sugars glucose, sucrose and lactose, people can't digest cellulose. The human digestive system uses special proteins called enzymes to break sugary polymers down into their simple glucose components. We then use glucose as a source of energy. For example, the enzyme sucrase breaks down sucrose, and lactase breaks down lactose. Our bodies do not produce cellulase, the enzyme that breaks down cellulose.

A termite (top) next to a gut from
A termite (top) next to a gut from
John Breznak/Michigan State University/NSF

Termites don't produce cellulase, either. Instead, they rely on microorganisms that live in a part of their digestive system called the hindgut. These organisms include bacteria and protozoans. They live in a symbiotic relationship with the termites -- neither the termites nor the microorganisms could live without the other.

The types of organisms found in the hindgut divide termites into two rough categories. Higher termites have bacteria in their gut but no protozoans, while lower termites have bacteria and protozoans. You can also categorize termites by where they live. Subterranean termites build large nests underground. Many primitive termites form colonies in the wood they are consuming.

A termite colony is essentially a multigenerational family. We'll look at termites' reproductive cycle and how it allows them to form large colonies next.

Termite Reproduction

If you've ever seen live termite workers or looked at a picture of termites in their nest, you've probably gotten the impression that they look almost larval. They don't have hard exoskeletons like many insects do. Instead, they look soft and milky. Termites look larval because, in a lot of ways, they are larval. The only fully mature termites in an entire colony are the king and queen. Even the other reproductives are neotonic -- they are sexually mature but have larval qualities.

This perpetual larval state gives termites a lot of flexibility. Basically, all termites start as eggs, and all eggs are capable of developing into any caste. The eggs hatch into larvae, and through a series of molts, the larvae develop into workers. The workers can undergo a two-stage molt and become soldiers. Older termites can even undergo regressive molts and go back to an earlier stage.

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When it's time for a colony to swarm, some workers molt into winged adults called alates, from the Latin word for "wing." The alates gather at an entrance to the colony and prepare to make their only flight, known as a nuptial flight. Their bodies harden and darken with exposure to the air. They begin to resemble winged ants.

Photo by China Photos,Getty Images A termite queen on display at the Chonquing Termite Control Institute

Termites usually swarm in the spring when the air is very humid and still, often just after it's rained. Many species swarm simultaneously, even if their colonies are separated by long distances. Scientists are not sure how this happens, but they suspect that it helps improve genetic diversity by allowing termites from different colonies to mate. This is especially important because most of the alates do not live to bear young. Instead, they become food for birds, toads and other animals.

After a male and female alate form a pair, they land and break off their wings. At this point, they're called dealates. They look for shelter, typically in a small hole or depression that's near both soil and wood. They seal this nest with saliva, soil and their own waste. Then, they mate, and the new queen lays eggs.

The king and queen care for the first generation of the new colony on their own until they've raised enough workers to take over the job. Workers expand the nest, and the queen's abdomen enlarges so she can lay more eggs. It takes two to four years for the colony to mature, and then the cycle starts again with a new set of alates swarming to form new colonies.

In addition to laying eggs, the king and queen produce pheromones that help regulate life in the colony. These pheromones determine how many larvae become workers, soldiers and alates. If the king or queen dies, these pheromones disappear. Then, one of the secondary or tertiary reproductives becomes the new primary reproductive, sometimes after killing off the competition. Queens can live up to 25 years, while most workers live between two and five years.

Termite colonies can survive for a long time, and in some species, queens lay thousands of eggs every day. For these reasons, termite nests can be enormous. Next, we'll take a look at where termites live and how they build their homes.

Termite Society

Giant termite mounds mark the
Giant termite mounds mark the
Photo by Carl D. Walsh/Aurora/

All social insects have some method for building a home. Honeybees build hives from wax, wasps build paper nests and bees dig tunnels in the ground. All termite species build nests, also known as termitaries or termitaria, but the specifics of these nests can vary.

Many primitive species build their nests in the food they're consuming. Scientists categorize these termites according to the type of wood they prefer -- damp, rotten or dry wood. In some cases, termites share their homes with fungi and bacteria that destroy wood. Termites often line these nests with particles of soil glued together with saliva, which helps the nests retain moisture and warmth. These colonies aren't particularly mobile, and when the wood runs out, the colony dies.

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Subterranean termites dig large networks of galleries and tunnels underground. Galleries are used for food storage and for raising larvae. These underground networks give the colony a place to live, and they can connect the colony directly to sources of food, like the roots of decaying trees or the side of a person's house. If there's an obstacle between subterranean termites and a food source, they will often build shelter tubes, or extensions of their tunnels. Shelter tubes are usually about the diameter of a pencil, and they're made of soil glued together with termites' saliva.

A termite nest on a palm tree at
A termite nest on a palm tree at
Photo by Tim Graham/

An underground network of tunnels gives subterranean termites some flexibility in where they live. If the weather gets cold, workers can dig deeper into the soil in search of warmth. The same is true in times of drought. If it gets hot, the colony can move to parts of the nest that are shaded by aboveground structures and vegetation.

Since they're concealed in wood or underground, the nests of primitive and underground termites can be hard to locate. Termite mounds are another story. These dome- or tower-like structures can be taller than a person. They are made from particles of soil and termite excrement glued together with workers' salivary secretions. Some species build mound-like nests on the sides of stumps, trees or poles.

The typical mound has multiple chimneys and tubes that allow air to circulate through the structure. The inner layers of the mound contain galleries in which the termites live and raise young. The king and queen usually live deep inside the mound, where they are well protected from predators and the elements. Some mound-building termites, particularly those in the subfamily Macrotermitinae, are gardeners. They use underground galleries to grow symbiotic fungi.

Termite mounds are strong -- they can survive fires and floods, although water can enter the inner chambers through the ventilation shafts and drown the termites inside. Concealed nests also offer termites protection from weather and predators. But neither type of nest is invulnerable. Animals like aardvarks, anteaters and pangolins have strong claws that allow them to dig into termite nests. Birds, bats, primates and even people also use termites as a food source. This is one reason why termites play an important part in many ecosystems -- they act as food for other animals. Next, we'll take a look at some of the other ways termites benefit ecosystems.

Termite Prevention

Termites eat dead wood. Without them, dead trees and brush wouldn't decompose normally.
Termites eat dead wood. Without them, dead trees and brush wouldn't decompose normally.
© Photographer:

Many people think of termites as aggressive destroyers of homes and property, but about 90 percent of termite species are beneficial. They consume, digest and make use of dead and dying vegetation. Some species also eat the waste of herbivores, which can contain undigested cellulose. In some places, termites are the most important factor in breaking down cellulose. Without them, dead trees and herbivore waste wouldn't decompose normally -- they would gradually pile up, making it harder for animals to migrate and find food.

Many homes and other human structures fit the bill for termite food because they're made of dead wood. Termites can't differentiate between the inside of a dead tree and the walls of a person's house. In some parts of the world, termite attacks on homes are so prevalent that people have adapted, building their homes on stilts lined with termite deterrents, like pieces of metal and pie pans.

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Fortunately, there's a lot people can do to prevent termite infestation. The process begins even before a builder starts to work on a house. Professional pest-control companies can treat the ground at the building site with a substance that kills or repels termites. This treatment usually offers protection against termites for at least five years. Builders can also construct houses in a manner that deters termites from entering. This basically involves making sure wood doesn't come into direct contact with soil. Other techniques include placing a moisture barrier under basements to help keep the area dry and removing piles of soil from under porches. A termite inspection is usually part of the home-buying process, which reduces your likelihood of buying a home that is already infested.

These steps don't guarantee that a home will never experience an infestation. Next, we'll explore how to detect the presence of termites.

Termite Infestations

Termite treatments and good building methods can't completely prevent a termite infestation. Homeowners in termite-prone areas have to keep an eye out for signs of the wood-eating insects. Often, the first sign of infestation is the emergence of a swarm. If you find alates inside your home, they probably came in through your walls. This is a sure sign that there are termites in your home. However, if you find a swarm outside, particularly if it's coming from a stump or a tree, the infestation may not have reached the building. Alates can look a lot like ants -- here's how to tell the difference:

  • Ants have a narrow waist. Termites do not.
  • Ants' front wings are significantly longer than their back wings. Termites' wings are the same length, and they can fold straight back down the length of the termite's body.
  • Ants' antennae are bent. Termites' antennae do not bend, and they look like a very fine string of pearls.

Here are some other common signs of home termite infestation:

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  • Wings: Alates shed their wings just after swarming. When the alates are inside your home, they typically shed their wings on windowsills or near lights.
  • Decayed wood: Termite damage generally follows the grain of the wood. Termites also line the damaged wood with soil. Damage from other sources, like water or fungus, doesn't follow this pattern.
  • Shelter tubes: Termites will dig tubes up cinderblocks, concrete, brick and other surfaces in order to get to wood. Sometimes, if you break the tubes open, you will see live termite workers inside.
© Photographer:

Termite damage happens from the inside out, so it can be hard to detect an infestation. If the wood in your house sounds dull when hit with a hammer, there may be termite activity inside. You can also use a screwdriver or ice pick to carefully probe anywhere you believe termites might be hiding. This can reveal damaged wood and the termites themselves.

Treating a termite infestation requires a professional exterminator. Next, we'll take a look at the most common methods used to get rid of termites.

Exterminating Termites

Termites can devour the wood in a home,
Termites can devour the wood in a home,
Photo by Peter Essick/Aurora/

If you discover an infestation of fleas or roaches in your home, you can often take care of it with over-the-counter products. This is not the case with a termite infestation. Although some of the chemicals that kill fleas and roaches will also kill termites, applying them to a termite infestation requires special tools and training.

When an exterminator comes to your home, he will first verify that termites are the culprit. Other insects, including carpenter bees and some species of ants, can also damage wood homes. Some people may also mistake water damage for termite damage. An exterminator will use tools like long probes, heat sensors, sound sensors, infrared cameras, hammers and drills to look for termite damage.

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If the exterminator finds conclusive signs of termites, he may use one of three treatment methods:

  • Baits are wood, cardboard or other cellulose-containing products soaked in a pesticide. Termites eat the baits and carry particles back to their nests, poisoning the rest of the colony.
  • Repellents discourage termites from entering a particular area. These can help keep termites from colonizing a new site in your home.
  • Termaticides kill the termites. Sometimes, exterminators have to pump hundreds of gallons of termaticide into termite nests in an attempt to treat the infestation. Another tactic involves applying an insecticide around the entire perimeter of the home and at every possible termite entry point. This keeps termites from getting inside, and any that are already inside usually die of dehydration.

Fortunately, it takes years for termites to do significant damage to a home. So if you discover an infestation on your property, you have time to get estimates from several exterminators. Before making a decision, find out what kind of warranty or guarantee the exterminator offers and whether you will have to pay for further treatments if the termites reappear. It's also a good idea to contact your local cooperative extension office to learn how your state governs termite control. That way, you can make sure that the exterminator you choose is properly licensed and qualified.

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More Great Links

Sources

  • Australian Museum. "Termits." (8/24/2007) http://www.austmus.gov.au/factsheets/termites.htm
  • Dr. Don's Termite Pages http://www.drdons.net/whatr.htm
  • Gold, Roger E. "Subterranean Termites." Texas Agricultural Extension Service (8/24/2007) http://insects.tamu.edu/extension/bulletins/b-6080.html
  • Homeostasis in Termite Colonies (8/24/2007) http://www.esf.edu/efb/turner/termite/social%20homeostasis.htm
  • Houglin, Andy. "Macrotermes bellicousus." Insecta Inspecta. (8/24/2007) http://www.insecta-inspecta.com/termites/macrotermes/index.html
  • Kamble, Shripat T. "Termites." University of Nebraska: Lincoln (8/24/2007) http://www.ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=338
  • Koehler, P.G. and C.L. Tucker." Subterranean Termites." University of Florida. (8/24/2007) http://edis.ifas.ufl.edu/IG097
  • LSU Agricultural Center. "Formosan Termites." (8/24/2007) http://www.lsuagcenter.com/en/environment/insects/Termites/formosan_termites/
  • Meyer, John R. "Termites." General Entomology. N.C. State University. (8/24/2007) http://www.cals.ncsu.edu/course/ent425/tutorial/Social/termites.html
  • PBS. "Termite Teamwork." (8/4/2007) http://www.pbs.org/wnet/nature/triumphoflife/multimedia/termite.swf
  • Penn State. "Entomological Notes: Eastern Subterranean Termites." (8/24/2007) http://www.ento.psu.edu/extension/factsheets/termite.htm
  • Smith, Robert L. "Termites. "Arizona-Sonora Desert Museum. (8/24/2007) http://www.desertmuseum.org/books/nhsd_termites.html
  • Suiter, Daniel R. et al. "Biology of Subterranean Termites in the Eastern United States." Ohio State University. (8/24/2007) http://ohioline.osu.edu/b1209/index.html
  • University of Kentucky. "Termite Control: Answers for Homeowners." (8/24/2007) http://www.ca.uky.edu/entomology/entfacts/ef604.asp
  • University of Toronto. "Order: Isoptera." (8/24/2007) http://www.utoronto.ca/forest/termite/iso1.htm
  • University of Toronto. "Termites 101." (8/24/2007) http://www.utoronto.ca/forest/termite/trmts101.htm