TERMITES: Isoptera

PHYSICAL CHARACTERISTICS

Termites are the most primitive group of living winged insects that lay their eggs on land. Some scientific studies suggest that termites are most closely related to cockroaches. The most primitive cockroaches, wingless wood cockroaches from North America, closely resemble termites in their appearance and behavior. Similarly, the most primitive termites, Mastotermes darwiniensis from Queensland, Australia, look and act like cockroaches. The similarities between termites and cockroaches suggest that termites could be called "social cockroaches" and cockroaches could be called "solitary termites." However, there are major differences in overall body plan and wing structure. Still, it is very likely that termites and cockroaches had a common ancestor but then branched off into their own distinct groups a very long time ago.

Termites have a caste system, meaning that each member of a group has a different function within the group. Each "caste" is told apart from another by its size, form, and the ability or lack of ability to reproduce. The castes usually consist of workers, soldiers, and kings and queens. Only the kings and queens reproduce. Termite workers and soldiers are unable to reproduce. Termites are usually pale and soft-bodied. Their thorax, or midsection, is broadly attached to the abdomen, giving them a thick waist. They have short antennae (an-TEH-nee) with beadlike segments. The workers and soldiers might be either male or female. Worker termites have powerful jaws for chewing wood or other plant materials. Depending on the species, soldiers may have big heads with sharp, scissorlike jaws or smaller, pointed heads. They tend to be larger and darker and have heavier bodies than the workers.

Only the insects that reproduce have wings, mate, and lay eggs. The forewings and hind wings of these termites are the same size. Termites hold their wings flat over the body when resting. The wings of king and queen termites break off just before the point where they are attached to the thorax. Queens among the mound-building termites often have bloated, sausage-shaped abdomens and are basically egg-laying machines. They range in length from 2 to 4 inches (5.1 to 10.2 centimeters). Larvae (LAR-vee), or young termites, look like the adults.

GEOGRAPHIC RANGE

Termites are found in warmer regions of the world, especially in the tropics and subtropics, or regions that border on the tropics.

HABITAT

Most termites prefer to live in warm, humid climates, especially at low altitudes along river valleys and in coastal areas. Other species are found in mountain forests, deserts, and grasslands.

DIET

Although the best-known termites eat dead wood, others eat a wide variety of foods, including small bits of decomposed, or disintegrated, plants; leaf litter; dead grass; dung, or the waste material of animals; funguses, and lichens, or certain plantlike organisms that live together, as one. Some of these termite species are considered pests when their food-gathering activities include crops, such as corn.

Unable to digest plant materials on their own, wood-eating and plant-feeding termites must rely on tiny organisms in their stomachs to help them digest their food. This organism, a protozoan (proh-toh-ZOH-uhn), whose body is made up of only one cell, and the termite depend on each other for food. Some termites lack these microscopic partners and instead must grow their own fungus for food, or else they have special chambers in their stomachs populated with different kinds of bacteria, another type of tiny single-celled organism, that help with digestion.

BEHAVIOR AND REPRODUCTION

Termites lead secretive lives hidden in wood, underground, or in specially constructed tubes or nests. They seldom come out in the open, except to mate, but some species routinely search for food above ground. They are social insects that live in colonies with thousands to millions of individuals. Most colonies are made up of different castes (workers, soldiers, kings, and queens) that work together to expand and repair the nest, defend the colony, reproduce, and care for and feed the young.

A long-lived king and queen are usually at the head of each colony. The queen is the only member of the colony capable of laying eggs. Workers make up the majority of the colony's population. They build and repair the nest, hunt for food, and feed and groom other members of the colony. However, among primitive termites, there is no true worker caste. Instead, their wingless young perform the tasks of workers. Soldiers defend the colony from ants and other invaders by snapping their scissorlike jaws at the intruders, chopping them up into little bits. Others have very small mouthparts, but their heads are packed with special glands that produce sticky and poisonous fluids. Some of these termite soldiers have pointed heads that are used as spray nozzles to direct a foul smelling, sticky glue at their attackers, gumming up their legs and antennae.

Termites rely on pheromones (FEHR-uh-mohns), special chemicals released from their bodies, to find one another and to communicate. For example, workers and soldiers have glands underneath the thorax that produce pheromones that compel others nearby to help repair damages nest walls. Species that tunnel through the soil create chemical trails underground so that their nest mates can follow them to food.

Termites spend a lot of time grooming, nibbling, and licking each other with their mouthparts. They also drink fluids from the tip of one another's abdomens, so they can pass along the microscopic organisms they need to help digest plant materials. Primitive termites live in or near their food source. The most familiar wood-feeding species nest in tunnels chewed in dead logs, stumps, and timbers. Some desert species live in the soil or under a protective papery coating that they build on the outside of the dead branches and trunks of desert plants. Other termites build their nests away from any food source. Their nests are constructed entirely underground, beneath rocks, partially above ground, or completely on the surface. Underground nests are usually made up of chambers or layers of tunnels, called galleries. The walls of the chambers and galleries are plastered with the hardened waste material of termites.

Species living in the open grasslands of Africa, Australia, and South America build cathedrallike mound nests on the surface, using mostly clay and their own waste droppings mixed with saliva as building materials. Some of these mounds are truly the skyscrapers of the insect world, reaching a height of 36 feet (10.9 meters) or more. The inside of these towering structures are filled with chambers, chimneys, and ventilation shafts that function as air conditioning to maintain fairly constant temperatures inside, no matter what the temperature is outside. With their walls almost as hard as concrete, these mounds are truly monuments, lasting for decades or even centuries.

In the tropics termites sometimes attach their lumpy or mushroom-shaped nests to tree trunks or high up on tree limbs. These nests are often linked to the ground by a series of tubelike runways. The materials used to make these mounds and tubes depend on the diet of the particular termite. Typically, they are made from chewed-up bits of plants, soil, and termite droppings, all mixed with saliva. Once dried, the nest walls feel and look like very coarse paper.

Each spring and summer thousands of winged kings and queens take to the air. They soon land, shed their wings, and begin the search for a mate from another colony. Some queens produce a pheromone to attract males. In some species, a pair of termites runs rapidly over the ground in a zigzag pattern during courtship, with the queen leading the way and the king following close behind. After courtship, the king and queen search together for a nesting site, usually in the soil or in a crevice (KREH-vuhs) or hole in wood. After clearing a small chamber and sealing themselves inside, they mate. All termites, whether they are male or female, develop from fertilized (FUR-teh-lyzed) eggs.

In other termite species, new colonies form by a process known as budding. Their sprawling colonies simply keep expanding into new territory, with new kings and queens moving to the edges of the continually expanding nest to start their own colonies. Their workers and soldiers mix freely with those of the original colony.

The king and queen tend to the first batch of young and actively join in nest building and other duties, but these tasks are taken over by the young termites as they mature. Young termites look like the adults when they hatch. They molt, or shed their external skeletons, several times before reaching adulthood, and they may or may not develop wings. Eventually, they and future generations take over all of the duties of the nest. Soon the queen's only job is to lay eggs. Some queens live as long as twenty years and lay millions of eggs during their lifetimes. In mature colonies, if the king or queen should die, he or she is quickly replaced by another king or queen already developing in the nest.

TERMITES AND PEOPLE

Most people think of termites as pests, and with good reason. Their feeding and nesting activities damage or destroy wood and wood products used in books, furniture, buildings, telephone poles, and fence posts, causing millions of dollars of damage every year. Millions of dollars more are spent trying to control their populations or get rid of them. Termite control methods include applying heat to infested areas, freezing them with liquid nitrogen, and zapping them with microwaves or electrical shocks. Each method is used for a particular kind of infestation. Lumber yards now treat much of the wood used in the construction of buildings with chemicals designed to repel termite attacks.

GOING FOR THE GOLD

A Canadian geologist, a scientist who studies rocks, visited Niger to look for the best sites to find gold. He had read that ancient African civilizations used termite mounds, sometimes 6 feet (1.8 meters) high and 6 feet across at the base, to locate deposits of the precious metal. Some termites dig down 250 feet (76 meters) below the surface and use gold-bearing soil to build their mounds. He managed to find a few mounds with gold, suggesting possible sites for further exploration.

Because of their ability to convert plant materials into animal protein, termites could be used to turn large amounts of raw plant waste into food for humans. The feeding activities of termites could be applied to breaking down sawdust and scrap lumber piling up in sawmills or eliminating straws, bean pods, and sugarcane pulp from food and sugar-processing plants. They might even be used to break down dried dung gathering in cattle feed lots and dairy farms. Raised on these waste products, the termites could then be fed to chickens and fish raised for human consumption. Raising large amounts of termites on these and other waste products is challenging and requires more termite research.

CONSERVATION STATUS

No termites are officially listed as endangered or threatened. With so much time and money invested in killing them, little consideration has been given to their conservation. In the tropics, termites are estimated to make up as much as 75 percent of the total weight of insects found in the forests and 10 percent of the total weight of all animals. Next to earthworms, termites represent one of the most important parts of any tropical habitat. They recycle vast amounts of plant material, making it available again as food for other plants and animals.

The widespread clearing and destruction of tropical forests for timber and farming have probably greatly cut down the populations of some termite species. The loss of termites affects not only the amount of plant materials converted into food for other organisms but also the numbers of birds, mammals, reptiles, insects, and spiders that depend on them for food and on their nests for shelter.

EASTERN SUBTERRANEAN TERMITE (Reticulitermes flavipes): SPECIES ACCOUNTS

Physical characteristics: Kings and queens measure 0.4 inches (10.2 millimeters) from head to wingtips. Their bodies are black, except for their yellow leg segments. Soldiers have a long, straight-sided, almost rectangular yellow head with a pale spot on top. Their thick, black, toothless jaws are strongly curved inward at the tips. Workers are about 0.2 inches (5.1 millimeters) long, with creamy white bodies.

Geographic range: These termites are native to the forests of the eastern United States, from Maine south to Florida and west to Minnesota and Texas; they were introduced into Canada in southern Ontario and Quebec.

Habitat: This species is found in deciduous (di-SID-joo-wus) hardwood forests, meaning forests of hardwood trees that loose their leaves in cold or dry weather.

Diet: Eastern subterranean termites eat the wood of many kinds of trees, preferring the outer portion of the trunk. Small, paper-thin layers of a dried paste made from their droppings divide their galleries. When working above ground in buildings and trees, they build protected tubes or shelters made from small bits of soil and saliva, lined inside with a paste made from their droppings.

Behavior and reproduction: Workers forage (FOR-ihj), or search, for food in shallow, narrow tunnels in the ground that connect stumps, logs, and roots. They also climb living trees to reach dead limbs or other areas with dead or rotten wood, and they attack landscaping items made of wood, such as fence posts, firewood piles, wood-chip mulch, scrap lumber, and flower planter boxes. From these items they invade nearby homes, sheds, and other structures. Since they feed inside exposed timbers or concealed wood frames, they can cause considerable damage over the years before they are found.

These termites do not build a nest structure. Instead, large, mature colonies consist of loosely connected galleries occupied by an extended family, with several kings and queens producing broods that contribute to the overall colony. Colonies expand, shrink, and move as foraging areas run out of food and new sources are found. The termites make their egg and nursery chambers inside logs, stumps, and other large items of wood that have plenty of moisture. Timbers in homes and other buildings are usually dry, and termites seldom use them as sites for their egg laying or for raising their broods. In winter they move down into the soil, beneath the frost line.

Eastern subterranean termites and people: This is one of the most important and destructive termite pests in eastern North America. Hundreds of millions of dollars are spent every year to control them and repair the damage they do. Shelter tubes crossing over the foundation of a structure are the clearest signs of their presence in homes and other buildings.

Conservation status: This species is not endangered or threatened. ∎

BLACK MACROTERMES (Macrotermes carbonarius): SPECIES ACCOUNTS

Physical characteristics: This is the largest termite in Southeast Asia. Winged kings and queens are about 1.2 inches (30.5 millimeters) from head to wingtips, with a wingspan of at least 2 inches (50.8 millimeters). The bodies of both workers and soldiers are very dark, nearly black. Male workers are larger than female workers. The soldiers are all females, large or small, and have very sharp, swordlike jaws.

Geographic range: Black macrotermes live in Borneo and Southeast Asia, including Thailand, Cambodia, and Malaysia.

Habitat: Black macrotermes are found in flat lowlands and are seen less often in hilly areas. They are especially common in coastal forests, but they also live on coconut and rubber plantations.

Diet: These termites collect mostly dead grass, twigs, and other plant debris (duh-BREE). These plant materials are hauled below ground into the nest. Small workers chew up the material, eat it, and then deposit their droppings as fertilizer on masses of spongelike fungus. The spores, or reproductive bodies that sprout on the outer surface of the fungus, are then fed to the younger termites in the colony. Older termites eat the remains of old fungus.

Behavior and reproduction: Colonies build large mounds up to 13 feet (4 meters) high and 16 feet (5 meters) wide at the base. The fungus is usually grown in large chambers around the edges of the mound.

Smaller workers spend all their time in the nest, caring for the king and queen, feeding the young, and repairing the nest. Larger workers and some soldiers hunt for plant materials on the ground at night. Foraging parties visit a new area every night. Major workers build paved tracks from the mound to the foraging area. Workers follow the track and then fan out to collect dead grass and twigs, with both large and small soldiers standing guard nearby.

The king and queen live in a special thick-walled cell inside the mound. The abdomen of the queen grows to extremely large proportions as it fills up with eggs. When the king and queen die, the colony may also die, unless there are other winged kings and queens already present in the colony to act as replacements.

Black macrotermes and people: This species does not have an impact on people or their activities.

Conservation status: This species is not endangered or threatened. ∎

BLACK-HEADED NASUTE TERMITE (Nasutitermes nigriceps): SPECIES ACCOUNTS

Physical characteristics: The queen is 0.7 inches (17.8 millimeters) in length, without wings. Her body is mostly reddish yellow, and the abdomen is very large. Soldiers have very dark heads covered with short, bristling hairs. Workers come in two sizes. Both large and small workers have dark bodies and rectangular heads.

Geographic range: These termites range from Mazatlán in western Mexico south to Panama and northern South America.

Habitat: Black-headed nasute termites are found along coastal plains, from sea level to about 3,280 feet (1,000 meters).

Diet: This species feeds on wood, mainly above the ground. The termites build extensive networks of broad tubes along the lower sides of tree branches.

Behavior and reproduction: Colonies live in large paperlike nests that are visible on trees, fence posts, and poles. A single colony may have more than one nest. Each colony is headed by a king and queen.

Black-headed nasute termites and people: This species occasionally attacks homes and other buildings.

Conservation status: This species is not endangered or threatened. ∎

LINNAEUS'S SNAPPING TERMITE (Termes fatalis): SPECIES ACCOUNTS

Physical characteristics: Kings and queens are brown and measure about 0.3 inches (8.5 millimeters), including wings. The soldiers are long and pale yellow. Their heads are straight-sided and have a small hornlike bump toward the front. They have long and slender jaws.

Geographic range: This species is found in northeastern South America, including Guyana, Suriname, Trinidad, and Brazil.

Habitat: This species lives in tropical forests.

Diet: The structure of their jaws suggests that they eat bits of decaying plants and soft, rotten wood.

Behavior and reproduction: The soldiers are thought to use their long jaws to anchor their bodies in the tunnel to block invasions by ants and other predators. Very little is known about their nesting behavior. They use their own waste to build their turret-like nests. This building material dries to form a dark, hard wall.

Nothing is known about their reproductive behavior.

Linnaeus's snapping termites and people: This species is the first termite ever to receive a formal scientific name.

Conservation status: This species is not endangered or threatened. ∎

WIDE-HEADED ROTTENWOOD TERMITE (Zootermopsis laticeps): SPECIES ACCOUNTS

Physical characteristics: This is the largest and most primitive termite in North America. Winged kings and queens measure 1.0 to 1.2 inches (25.4 to 30.5 millimeters) from head to wingtips, with a wingspan up to 1.9 inches (48.3 millimeters). Their bodies are dark yellowish. Soldiers measure 0.6 to 0.9 inches (15.2 to 22.9 millimeters) in length. The flattened head is widest at the back, and they have very long and roughly toothed jaws. Workers, soldiers, and other castes are whitish yellow or cream in color.

Geographic range: In the United States these termites are found from central and southeastern Arizona to southern New Mexico and western Texas; they also live in Chihuahua and Sonora, Mexico.

Habitat: This species lives in dry habitats between 1,500 and 5,500 feet (457 and 1,676 meters) along canyons and river valleys. The termites are found inside the rotten cores of logs and large branches of living willows, cottonwoods, sycamores, oaks, alders, ash, walnuts, hackberries, and other hardwoods.

Diet: Wide-headed rottenwood termites feed only on rotten hardwoods. Unlike many other termites, this termite is not known to feed on completely dead and rotten logs or on pines, firs, and their relatives.

Behavior and reproduction: Colonies are found in galleries and open chambers in rotten wood. The chambers eventually become filled with masses of termite waste. The termites sometimes gain access to a rotten tree core through a knothole. These and other knotholes are plugged with termite waste in the form of hardened pellets. Inside, the galleries are usually quite damp. Soldiers with powerful jaws defend the colony against ants and other predators.

Kings and queens fly in the middle of the night from late June through early August. Mated pairs look for tree scars, knotholes, or small pockets of rot or other wounds in trees, where they can gain access to the rotten core. A single king and queen usually head each colony, but there may be additional termites that can reproduce and contribute broods to the colony. Colonies are small and rarely have more than one thousand individuals.

Wide-headed rottenwood termites and people: This species attacks living trees, quickening their collapse and death from rot on the inside. However, they are not considered pests because the trees they attack are not used for lumber.

Conservation status: This species is not endangered or threatened. ∎

FOR MORE INFORMATION

Periodicals:

"Geographica: African Termites Guide Way to Gold." National Geographic 190, no. 6 (December 1996).

"Geographica: Glow-in-the-Dark Colors Expose Termite Secrets." National Geographic 184, no. 5 (November 1993).

Prestwich, G. D. "Dweller in the Dark: Termites." National Geographic 153, no. 4 (April 1978): 532–547.

Web sites:

"Critter Catalog: Termites." BioKids. http://www.biokids.umich.edu/critters/information/Isoptera.html (accessed on September 9, 2004).

"Isoptera: Termites." Ecowatch. http://www.ento.csiro.au/Ecowatch/Insects_Invertebrates/isoptera.htm (accessed on September 9, 2004).