Termite

• 1. Introduction

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  In the northern part of Kruger National Park, about 1.1 million active termite mounds can be found. Yet most termites in the world are almost never seen. Termites are social insects that feed on decaying plant matter, mostly wood, leaf litter and soil humus. About 2,997 species have been described. Their colonies range from a few hundred individuals to enormous societies of several million, and most species spend nearly their whole lives hidden inside tunnels and galleries.

  Why do people call them white ants when they are not ants at all? How does a colony of millions run itself with no ruler giving orders? What allows an animal to live on wood? And how can insects that recycle whole forests also bring down the beams of a house?

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• 2. Cockroaches in Disguise

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  In 1925, researchers first suggested that termites were close relatives of the wood-eating cockroaches of the genus Cryptocercus, also called the woodroach. Their evidence was a likeness between the symbiotic flagellates living in the guts of both groups. In the 1960s, F. A. McKittrick noticed similar body features in some termites and young Cryptocercus. In 2008, DNA analysis of 16S rRNA sequences placed termites deep inside the cockroach order, Blattodea, with Cryptocercus as their closest relative.

  That result ended a long run as a separate order named Isoptera. The name comes from the Greek words for equal and winged, because a termite's fore and hind wings are nearly the same size. Today termites are often treated as an epifamily called Termitoidae inside the cockroach order.

  Cryptocercus explains why the link makes sense. Most cockroaches are not social, but this genus cares for its young and grooms its companions. Termites took that family habit much further.

  The nickname white ants comes from the pale, soft-bodied, unpigmented workers. The word termite itself traces back to the Latin termes, meaning woodworm or white ant, bent by the influence of terere, which means to rub, wear or erode. English speakers first used it in 1781. Earlier names such as wood ants or white ants may never have been widely used, since termites do not live in the British Isles.

  The resemblance to real ants is shallow. Both groups became social through convergent evolution, and termites were the first social insects to develop a caste system, more than 100 million years ago.

  Fossils push the family tree back even further. In 2024, a stem-termite genus called Sociala was identified from the Karabastau Formation, which dates to the Middle to Late Jurassic. An extinct mammal-like animal called Fruitafossor, from the Morrison Formation, had a body resembling modern termite-eaters, which hints that it ate termites. The oldest known termite nest comes from the Upper Cretaceous of West Texas, where the oldest known faecal pellets were also found.

  Some researchers argue for a far earlier start. F. M. Weesner proposed that the family Mastotermitidae reaches back to the Late Permian, 251 million years ago. He pointed to fossil wings from Permian layers in Kansas. Kumar Krishna and colleagues reject this and say the Paleozoic and Triassic insects tentatively called termites are unrelated.

  The living giant northern termite, Mastotermes darwiniensis, still keeps cockroach habits that other termites dropped. It lays its eggs in rafts.

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• 3. Castes and Crowns

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  Termites pass through an incomplete metamorphosis, moving from egg to nymph to adult. Ants, bees and wasps change completely and stay flexible only as larvae. Young termites stay flexible through many molts, which lets the colony shape juveniles into different castes. As a result, most of the labour is done by juveniles rather than adults.

  Early instars are totipotent, meaning they can molt into any form. With each molt the options usually narrow, until the final instar is committed and works as an adult. Basal families such as Archotermopsidae stay flexible even in late instars.

  Two broad paths exist. In the linear pathway, every immature can become a winged adult, and soldiers are the only truly sterile caste. In the bifurcated pathway, young split at the egg or within the first two instars into a winged line and a wingless line. That choice cannot be undone. The wingless line supplies sterile workers and soldiers. The winged line supplies the reproductives. The split is found mainly in the Neoisoptera, and is thought to have evolved as species began foraging away from their nests instead of living inside their food.

  Workers forage, store food, and tend the brood and the nest. In ants, bees and wasps the workers are all female, but termite workers are diploid and can be male or female. In wood-nesting families such as Archotermopsidae, the workers are fertile and undifferentiated, and are called pseudergates. Sterile true workers are the most derived form.

  Soldiers exist only to defend. Many have heads and jaws so large that they cannot feed themselves, so workers feed them.

  The primary reproductives are the king and queen, who form a lifelong pair. Ant males die soon after mating, but a termite king keeps mating with the queen for life. Winged reproductives leave the colony only during a nuptial flight. Its timing depends on the species, the time of day, moisture, wind speed and rain. Some swarms emerge at dusk and gather around lights, and the swarms draw many predators.

  The winged termites are poor flyers. They launch themselves and head off in a random direction. After landing, a pair digs a chamber big enough for both, seals the entrance and mates. They may never surface again.

  In the earliest days, the queen lays only 10 to 20 eggs. When the colony is several years old she may lay as many as 1,000 a day. In some species a mature queen has a hugely swollen abdomen and may produce 40,000 eggs a day, with some 2,000 ovarioles in each of her two ovaries. Attendant workers help her move. Queens can live 30 to 50 years.

  If the queen is missing, the king releases pheromones that encourage the development of replacement queens. Supplementary reproductives can also take over when a primary dies or is cut off from the colony. Pheromones keep all but a very few termites from ever becoming fertile.

  The neotropical termite Embiratermes neotenicus has a stranger system. A colony may hold a primary king with up to 200 neotenic queens, all produced by parthenogenesis from the founding queen. This form of asexual reproduction preserves heterozygosity, which avoids inbreeding depression.

  Queens of Reticulitermes speratus live long without losing fertility. They show much less oxidative DNA damage than workers, soldiers and nymphs, apparently because of extra catalase, an enzyme that guards against oxidative stress.

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• 4. Decay Eaters

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  Newly hatched termites carry none of the microbes they need to digest wood. They acquire them when nestmates feed them a culture. In the lower termites, this community includes flagellate protists such as Trichonympha. These single-celled gut dwellers rely in turn on bacteria embedded on their own surfaces for some of their digestive enzymes.

  Workers pass food and gut microbes through feeding, either from the mouth or the anus. This is called trophallaxis. It recycles nitrogen-rich material and means parents need to feed only the first generation of young. That lets colonies grow much larger, and it ensures the symbionts pass from one generation to the next.

  Spirochetes in termite guts can fix nitrogen from the air into a form the insect can use. Gut bacteriophages resemble phages found in the human gut. Scientists describe their grasp of the whole digestive partnership as still rudimentary.

  In the higher termites, the family Termitidae, the insects make some of their own cellulase enzymes. They still depend mostly on bacteria, and the flagellates have been lost. Lower termites mostly eat wood and prefer fungus-infected wood, which is easier to digest and rich in protein. Higher termites eat a wider menu that includes faeces, humus, grass, leaves and roots.

  Wood choice matters. Moisture, hardness, and resin and lignin content all change how readily wood is attacked. In one study, the drywood termite Cryptotermes brevis strongly preferred poplar and maple over other woods.

  Some termites grow their own food. The subfamily Macrotermitinae keeps gardens of the fungus Termitomyces, nourished by termite excrement. Spores pass unharmed through the termite gut and germinate in fresh pellets, which completes the cycle. Molecular evidence suggests this farming began about 31 million years ago. It is assumed that over 90 per cent of dry wood in the semiarid savannahs of Africa and Asia is reprocessed by these termites. Originally rainforest dwellers, they used farming to colonise the African savannah and then spread into Asia.

  The scale of this appetite shows in the numbers. In some tropical regions termites are estimated to make up 10 per cent of animal biomass. Termites and ants together are about 1 per cent of insect species but more than 50 per cent of insect biomass. Termite breakdown of cellulose is also thought to produce 11 per cent of atmospheric methane.

  Africa holds roughly 1,000 species, South America over 400, Asia 435 and Australia over 360. Europe has about 10 and North America about 50. In China, termites live only in the mild tropical and subtropical regions south of the Yangtze River.

  Termites avoid cool and cold habitats because their cuticles are soft. Protection against drying out and against attackers comes from the shelters they build.

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• 5. Mounds and Tubes

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  Species in the genus Macrotermes build what may be the most complex structures in the insect world. Their mounds reach 8 to 9 metres in height and include chimneys, pinnacles and ridges. The tallest mound ever recorded was 12.8 metres, found in the Democratic Republic of the Congo.

  Nests fall into three types. Hypogeal nests lie wholly underground. Epigeal nests, which are the mounds, rise above the soil. Arboreal nests sit above the ground but stay linked to it by shelter tubes. Most termites actually build underground colonies rather than grand mounds. Primitive termites nest inside logs, stumps and dead parts of trees, as their ancestors did millions of years ago.

  Builders use faeces, partly digested plant material and soil. Carton nests, made from faecal and wood material, are an arboreal style. Carton from mangrove-dwelling Nasutitermes is rich in lignin and poor in cellulose, because gut bacteria have already worked on it. In Puerto Rican mangrove swamps, arboreal termite nests can account for as much as 2 per cent of above-ground carbon storage.

  No single termite directs any building project. Instead, a pellet of soil or a pillar prompts one termite to add to it, and that addition encourages others. The information that guides the work lives in the changing structure, not in direct contact among individuals.

  The compass termite, Amitermes meridionalis, builds wedge-shaped mounds up to 3 to 4 metres tall and 2.5 metres wide. The long axis points roughly north-south. Experiments show this orientation helps regulate temperature. The inside warms quickly in the morning, avoids overheating at midday, and then holds a plateau through the afternoon.

  Mounds also have defensive design. Cubitermes colonies build narrow tunnels that a single soldier's head can block. A heavily protected chamber called the queen's cell houses the king and queen as a last line of defence. Clay-rich mounds can erode in torrential rain, while carton nests can withstand heavy precipitation. Some species build polycalic nests, which are several nests joined by underground chambers.

  Shelter tubes, also called mud tubes, start from the ground and climb walls. Termites build them at night, when humidity is higher. They keep the air humid and dark, and they protect workers from ants in particular. These tubes are made from soil and faeces, and can be under 1 centimetre wide up to several centimetres wide. Some run for dozens of metres.

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• 6. Alarms and Sacrifices

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  Most worker and soldier termites have no eyes at all. A few species, such as Hodotermes mossambicus, have compound eyes used to tell sunlight from moonlight. For the rest, antennae do the work of touch, taste, smell, heat and vibration.

  The commonest form of communication is antennation, backed by a set of pheromones. Contact pheromones pass during feeding and grooming. Alarm pheromones come from the frontal gland, trail pheromones from the sternal gland, and sex pheromones from the sternal and tergal glands. Each colony has its own odour, shaped by genes, diet and gut bacteria. Hydrocarbons on the cuticle let termites recognise outsiders.

  Foraging follows chemical signals. In Nasutitermes costalis, soldiers scout first. Workers then arrive in large numbers, and soldiers thin out. Isolated workers may search by Lévy flight, a movement pattern useful for finding nestmates or food.

  When a tunnel is breached, soldiers bang their heads, which seems to summon other soldiers and recruit workers to repair the damage. An alarmed termite bumps into others and spreads the alarm. If the hole is wider than a soldier's head, soldiers form a phalanx-like ring and bite intruders.

  Soldier weapons vary widely. Mandibulate soldiers use jaws that bite and crush, as in Incisitermes. Others slash, as in Cubitermes, or snap, as in Termes. Armitermes soldiers pierce. Cryptotermes soldiers have globular heads that plug narrow tunnels. Nasute soldiers have lost their mandibles and instead spray sticky secretions containing diterpenes from a horn-like nozzle. Formosan subterranean termites are known to secrete naphthalene to protect nests.

  Some defence ends in death. Soldiers of Globitermes sulphureus rupture a gland beneath the cuticle. Its thick yellow fluid turns sticky in the air and tangles invading ants. Workers of Neocapritermes taracua form a pouch of chemicals and burst, paralysing enemies. Serritermitidae soldiers rupture between head and abdomen to plug nest entrances. In Coptotermes formosanus, termites squeeze into foraging tunnels and die, blocking the passage and ending a fight with a rival colony.

  Rival colonies always meet with aggression. Fights can kill on both sides and shift territory, and some colonies bury their dead in cemetery pits. Macrotermes bellicosus and Macrotermes subhyalinus, by contrast, are not always hostile. Where neotenic queens compete for control, all but one are eliminated.

  Termites deal with their dead by burying them, eating them or avoiding them. Sometimes they carry a body out of the colony, a habit called necrophoresis. They also avoid nestmates infected with spores of the fungus Metarhizium anisopliae, which warn of their condition through vibrational signals.

  In rare cases, a raid by the ant Megaponera analis succeeds in destroying an entire colony.

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• 7. Enemies and Lodgers

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  A single aardwolf can eat thousands of termites in one night. It finds them by sound and by the scent that soldiers release, and it collects them with a long sticky tongue. One termite species, Hodotermes mossambicus, was reported in 1990 in the stomachs of 65 birds and 19 mammals.

  Other predators include aardvarks, anteaters, bats, bears, echidnas, foxes, numbats and pangolins. Sloth bears break open mounds. Chimpanzees have developed tools to fish termites from their nests. Wear patterns on bone tools used by the early hominin Paranthropus robustus suggest they dug into termite mounds.

  Ants are the greatest enemy. Megaponera is a strictly termite-eating genus that mounts raids, some lasting several hours. Paltothyreus tarsatus carries as many termites as it can in its mandibles while recruiting nestmates along chemical trails. Scouts of Tetramorium uelense recruit 10 to 30 workers and immobilise small termites with a sting. Subterranean army ants such as Dorylus commonly prey on young Macrotermes colonies. Some wasps, including Polybia and Angiopolybia, raid mounds during nuptial flights.

  Termites suffer parasites as well, including dipteran flies, Pyemotes mites and many nematodes. Fungi such as Aspergillus nomius and Metarhizium anisopliae threaten whole colonies because they are not host-specific. When parasite attack looms, a colony may migrate.

  Some other species move in or imitate. A fungus produces small brown balls known as termite balls, which mimic termite eggs, and workers sometimes tend them. Trichopsenius beetles make the same cuticle hydrocarbons as their Reticulitermes hosts, so they pass as colony members. The beetle Austrospirachtha mimetes has appendages on a swollen abdomen that let it pass as a termite worker.

  Some ants coexist peacefully with termites. Nasutitermes corniger forms associations with certain ants to keep predatory ants away. The earliest known association between Azteca ants and Nasutitermes termites dates to the Oligocene to Miocene. A total of 54 ant species are known to live in Nasutitermes mounds. Termitophiles such as certain beetles, caterpillars, flies and millipedes cannot survive outside termite colonies at all.

  Termites also visit flowers. The orchid Rhizanthella gardneri is regularly pollinated by foraging workers, and it may be the only orchid in the world pollinated by termites.

  Plants fight back with chemicals that reduce the ability of termites to digest cellulose. Seedlings are the weak point, since their defences develop only after the seedling stage.

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• 8. Pests and People

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  The Makiritare of the Alto Orinoco province of Venezuela eat termites as a delicacy and commonly use them as a spice. Termites also appear in traditional medicine for illnesses such as influenza, asthma and bronchitis.

  Termites are better known as pests. Of 3,106 known species, only 183 cause damage, and 83 cause significant damage to wooden structures. Regional counts of economically significant species are 16 in Australia, 26 in the Indian subcontinent, 24 in tropical Africa and 17 in Central America and the West Indies. The genus Coptotermes has the most pest species, 28 in all.

  Their habit of staying hidden means damage often goes unseen until only a thin outer layer of wood remains. Drywood termites travel in contaminated goods, containers and ships. Cryptotermes brevis is the most widely introduced invasive termite in the world and has reached every island in the West Indies and Australia. Termites can also damage food crops, and most attacks come in the dry season.

  In Australia, termites cost more than A$1.5 billion a year and cause more damage to houses than fire, floods and storms combined. In Malaysia, estimated property damage reached about RM400 million. In the southwestern United States, the yearly toll is approximately 1.5 billion dollars. The true worldwide cost cannot be determined.

  Control starts with regular inspection by a trained professional and with termite monitors made of wood or cellulose placed beside a structure. Treatments include copper-based substances such as Bordeaux mixture and chromated copper arsenate. In the United States, a licensed professional can apply a soil termiticide with the active ingredient Fipronil, approved by the Environmental Protection Agency for economically significant subterranean termites. Demand for natural alternatives has raised interest in methods such as orange oil.

  Plant-based products are also in use. In Australia, Blockaid is a paint-on, nontoxic barrier that uses a range of plant extracts. An extract of the Australian false sandalwood Eremophila mitchellii repels termites so strongly that they starve rather than eat food nearby.

  To track termite movements, researchers once baited colonies with rabbit or chicken IgG marker proteins and later tested field-collected termites. Cheaper options now use egg white, cow milk or soy milk proteins sprayed on termites and detected with an ELISA test. RNAi insecticides aimed at termites are in development.

  Termites also suffer from human activity. A study of three Caatinga sites in the semi-arid region of northeastern Brazil recorded 26 species. Diversity and abundance fell as disturbance rose, with wood-feeders hit hardest by tree loss, soil cover loss and trampling by cattle and goats.

  The distribution of most known pest species is expected to grow with climate change, and urbanisation and greater connectivity may widen the range of some pest termites.

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