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
, 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.
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:
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
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.
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 ***ually 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.
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.
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.
Giant termite mounds mark the
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
, 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.
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
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.
Worker termites often feed larvae regurgitated food, much the way birds feed their young. However, the larvae need to develop the ability to digest cellulose on their own -- they have to be exposed to the organisms that live in termites' digestive tracts. This usually requires the larvae to eat other termites' waste.