Imagine an enemy that can weigh more than 77 pounds (35 kilograms), can burrow as deep as 300 feet (100 meters) and can severely damage an entire building almost undetected in around three months. Now imagine this enemy is not so much one creature, as 10 million tiny creatures working in perfect harmony to destroy whatever they come across. That enemy is the Formosan subterranean termite, (one termite species of an estimated 4000), and once a population has been established in an area, it’s proven very very very difficult to eradicate.
The Formosan subterranean termite (Coptotermes formosanus) probably originated in China, though it was discovered in and named after Taiwan, then Formosa. Probably the most widespread and economically damaging termite species, it is now found in Japan, South Africa, Sri Lanka and across the southern part of the United States. But those living above 35° north latitude find themselves in an enviable position, as the termites’ eggs won’t hatch below about 68°F (20°C).
The Formosan termite’s social structure is similar to other termites’, just with much larger numbers. It has three castes: the reproductives, the workers and the soldiers.
The reproductive termites include the king, the queen and the alates. Alates are winged termites capable of swarming, reproducing and establishing new colonies. Formosan alates are yellowish-brown and around 0.5 to 0.6 inches (12-15mm) long. They have small hairs on their wings, which easily distinguishes a Formosan alate from other species.
The king and queen are a mating pair of alates who have founded a new colony. Though the king and queen will mate for life, they are not monogamous, and it is not uncommon to have several reproductive pairings in a colony.
The queen leads the colony and is the colony’s primary reproducing female. She can live up to 15 years and produce up to 2000 eggs a day, growing larger with each successive molt to the point of becoming practically immobile. She must then be cared for and assisted by the workers.
Formosan workers can live three to five years, and they make up the largest proportion of the population, outnumbering the soldiers 9 to 1. They do not look particularly unique, having the same whitish coloring and being only slightly larger than other termites.
The workers are responsible for finding and storing food, taking care of the nymphs and maintaining the nest. They are the termites usually found in wood, gathering cellulose to feed to other colony members. They digest the cellulose and feed the digested material to the other colony members either from the mouth or the anus. This feeding process, called trophallaxis, helps the colony grow quickly by removing the responsibility of feeding younger generations from the alates, allowing them to spend all their time and energy reproducing.
When building a nest, the workers use wood and soil, cemented with saliva and feces, to build the nests, or cartons. The cartons obviously provide a protected living space for the colony, but they also have chambers that collect water through condensation, highways that allow for optimal movement through the nest and tunnels that regulate the temperature and CO2 levels of the nest.
The soldiers, as the name suggests, protect the nest from invaders. Like the alates, they have a distinctive appearance – their red heads and whitish bodies make them easy to identify – and like the workers, the soldiers can live up to five years.
Each soldier can release defensive secretions from a fontanel in its head. This secretion is one of the few natural occurrences of naphthalene, a chemical found in mothballs, which is probably used to repel ants, poisonous fungi and nematode worms.
The soldiers are critical to the species’ success in the United States. The Formosan subterranean termite colony has many times more soldiers than indigenous termite colonies. Up to 15% of the Formosan colony is made up of soldiers, whereas only about 2% of native colonies are made up of soldiers. This superior protective force means the Formosan termite has been able to in some cases replace native termite colonies almost completely.
Building a new colony
When it grows large enough, a single colony may produce up to 70,000 alates. These alates will then swarm away to form new colonies. The females fly off first, immediately searching for nesting sites, with males following shortly thereafter.
The dispersal flights occur at dusk on calm, humid evenings in the spring and summer, from April to July. After a short flight, the alates shed their wings – that is, they physically break them off. Once they form a mating pair, the new king and queen find a crevice in damp ground or wood and hollow out the royal chamber, where the queen lays 15 to 30 eggs.
When the eggs hatch two to four weeks later, they are nursed by the king and queen. The king and queen continue to care for this first generation until that generation’s third instar [the number of instars before maturity]. One or two months after that, the queen lays the second batch of eggs, which the first generation of termites will nurse.
It can take between three and five years for a colony to reach the size where it can cause severe damage and produce alates.
Like most termites, the Formosan subterranean termite mostly eats cellulose-based materials like paper, wood and cardboard. The workers eat the cellulose material, and they rely on bacteria and flagellates in their guts to aid the digestion of the material. Interestingly, they can produce their own enzymes to digest the material, making their relationship with single-celled organisms unclear.
However they end up breaking down the food, one study, authored by Juan A. Morales-Ramos and M. Guadalupe Rojas, has shown Formosan termites can derive more nutritional benefits from some woods than others. This has been shown to influence the feeding preferences of termites. Colonies feeding on pecan and red gumwood, for example, produced more offspring, and those feeding on pecan and American ash had a higher survival rate of offspring.
Though it benefits most from eating certain types of wood, the Formosan termite can chew through a number of other materials, including foam insulation boards, thin lead and copper sheeting, plaster, asphalt and some plastics, to build foraging routes.
This ability to chew through so many materials – as well as the sheer size of the colonies – makes it much more economically destructive than other termites.
The Formosan termite causes damage everywhere it is established, but it costs US consumers $1 billion annually for prevention and repairs. The most destructive insect in Hawaii, it causes $100 million in damage in the state each year. In New Orleans, anywhere from one-third to one-half of the city’s 4000 live oak trees are infected, costing the city $300 million a year.
All of this has happened in the 60-odd years since World War II, when the termites were introduced to the United States, presumably on boats that first traveled to Hawaii and then to the continental US.
Points of entry
The Formosan termite generally enters a building from ground contact: expansion joints, cracks and utility conduits and any wood-to-ground contact make great entry points.
Since the colony-founding alates have wings, it’s not unusual for them to form aerial colonies if they find adequate conditions. This mostly occurs in flat-roofed high-rise buildings, where food and standing water are readily available – experts estimate up to 25% of infestations in urban southeastern Florida are aerial.
Infestations are usually fought on several fronts. The termites do not attack wood that has been pressure-treated with preservatives, though they can bypass treated wood to find the untreated.
Because the termites look for a combination of water and cellulose, fixing leaky plumbing and limiting air conditioning condensation can discourage them from establishing a nest or can force them to search elsewhere for a more habitable location.
Finally, professional exterminators can apply a soil treatment to repel the termites. The massive size of the colonies keeps this from being a fool-proof method, so it usually is used in conjunction with termite poison.
But the treatments have to be carried out quickly and on an enormous scale. One colony can be large enough to infest several houses, and unless the colony is killed off quickly and completely, the termites could reinfest an area that had been cleared.