|Printed Text = 7 pages|
|630 US ISSN 0271-9916||March 1990||RESEARCH EXTENSION SERIES 117|
HITAHR * COLLEGE OF TROPICAL AGRICULTURE AND HUMAN RESOURCES * UNIVERSITY OF HAWAII
Julian R. Yates III is an extension specialist in urban entomology in the Department of Entomology, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa.
Minoru Tamashiro is professor of entomology, emeritus, in the same department.
|1.||Flight slits in a wooden beam|
|2.||Wingless female and male adults in tandem|
|3.||A mature Formosan subterranean termite queen|
|4.||Formosan subterranean termite worker and soldier|
|5.||Winged adult swarmers (alates)|
Although the Formosan Subterranean Termite, Coptotermes formosanus Shiraki, was officially recorded in Honolulu in 1913, an old newspaper article indicates that it was already present in Hawaii in 1869. The article described damage caused by "white ants", but the description makes it obvious the damage was done by subterranean termites. (To distinguish this termite from ants and other termites, see Entomology Note No.4, available from the Department of Entomology, UHM.) The Formosan subterranean termite, which is commonly called the "ground" termite in Hawaii, apparently was introduced from Formosa or South China during the period when there was extensive trade in sandalwood between the Kingdom of Hawaii and China.
The termite has since spread to all of the major islands: Hawaii (1925), Kauai (1929), Lanai (1932), Maui (1933), and Molokai (1975). The original infestations on Maui and Lanai were eradicated, but the termite was reintroduced to both islands in the late 1940s or early 1950s. It is now found throughout most of Oahu and Kauai but is still limited to seaports or areas surrounding seaports on other islands. On Hawaii, it is found in Hilo, Kawaihae, and Kona; on Maui, in Kahului, and Wailuku, with isolated infestations in Maalaea and Kihea; on Molokai in Kaunakakai and Kalaupapa; and on Lanai at the Kaumalapau Harbor.
It is apparent that the priamry mode of transportation between islands has been by ship. Potential source materials include wooden skips or palettes, poles, wood from old homes, wooden packing crates, and similar items.
In spite of its relatively limited distribution, the Formosan subterranean termite is by far the most economically damaging pest in Hawaii. The cost to prevent or control infestations and to repair the damage caused by this pest has been conservatively estimated at more than $60 million a year. This cost will probably increase as the termite moves into areas in Hawaii where it does not yet occur, the colony density increases in areas where the termite does occur, the values of existing buildings increase, and additional buildings are constructed, putting more buildings at risk.
Much of the loss is due to the aggressive but secretive nature of attack by this pest. There will be little or no external evidence of attack. Often, the first indication of an infestation is a sagging floor or door, leakng roof, warped walls, hollow-sounding beam, discolored or blistered paint, depression in wood, moist area, springy floor or step, short circuit, telecommunication blackout, or similar problem. An infestation can cause great damage in a relatively short time because of the large numbers of aggressive individuals involved in the attack. Colonies of the ground termite in Hawaii average over 2 million individuals, with large colonies exceeding 10 million. Unprotected homes built over strong existing colonies have been almost completely destroyed in two years. Prevention and early detection of infestations, therefore, are critical with this pest. These require detailed knowledge of the biology and habits of this termite.
Major swarms of this termite occur in May and June, but small flights can occur at any time of the year. Swarming is the primary way the termite naturally spreads after it has been transported to a new area. Spread by swarming is slow, however, because the termite is a poor flier. Unassisted, it cannot fly more than 1/4-mile. Moreover, the swarmers are attracted to the closest light source, which is usually no more than 25-50 yards away.
Swarming starts just after sundown on warm, humid, nearly windless evenings. The primary environmental factor that determines whether the termites swarm is the windspeed at the flight slits (Figure 1). If the wind exceeds 2 mph, swarming will not occur. If swarming starts and the wind increases to more than 2 mph, swarming stops. On average, swarming lasts about 30 minutes. Swarming may occur over the entire island chain, over a single island, or on just parts of the island. Not all of the swarmers in a colony will swarm on the same night.
Swarmers are attracted to lights. In major swarms, thousands of termites can be seen around street lights or the lights in or around houses. After a short flight, the termites land on the ground and drop their wings. The wings break off close to the termites body when it folds them up and forward.
The wingless adults pair off and move about in tandem, with the male following the female (Figure 2). They are searching for a new place to live (physical niche). Fortunately, very few of the pairs survive to start new colonies. Most of the swarmers are eaten by geckos, spiders, chameleons, toads, ants, or other predators. Those that escape being eaten still have the problem of finding the right conditions to survive. These must include food, moisture, and shelter.
The termite's food, which is cellulose, is found in the cell walls of all plants. Therefore, any plant or plant product, such as wood, paper, canec, fruits, nuts, cork, or living plants, can serve. The termite's primary food, however, is wood. Surprisingly, the termite does not have the ability to digest cellulose. It lacks the enzyme required to break cellulose down into usable products. The cellulose eaten by the termite is broken down by symbiotic protozoa, or bacteria that lives in the termite's gut. Without these protozoa or bacteria, the termite would starve to death.
Moisture, the second requirement, can be fulfilled by high humidity. The termite does not require free water. Moisture can come from normal soil moisture, poor drainage, leaking roofs, or plumbing, condensation from air conditioners or pipes, water on poorly designed decks and roofs, or similar sources. Although the termite is able to survive on very small amounts of moisture, moisture is critical. This is why it swarms on warm, humid, windless evenings.
The third requirement is the physical niche. The pair cannot start on bare, smooth surfaces, even if the other two criteria are met. The swarmers require a joint, nail hole, crack, or similar crevice they can enter and seal to form a mating chamber. Fortunately, the combination of food, moisture, and physical niche, is difficult for the termite to find. Our goal, of course, is this to make it harder.
If all the criteria are met, the pair can start a new colony. The male and female mate within the sealed mating chamber. The first batch of 15-25 eggs is laid about five days later. The eggs hatch in 21-30 days. The newly hatched young must be fed predigested food by the parents, because they are unable to feed themselves. The jaws on young termites are not highly sclerotized (hardened), so they probably can only feed on semiliquid food. They remain in the nursey until they go through two molts. After this, they become functional workers in the colony and can leave the nursery to forage, but they will continue to molt and grow.
The queen then lays another batch of eggs. The second group and all subsequent offspring are fed by and acquire the protozoa from the workers in the colony. This process continues until a major colony, made up of 2 million or more termites, is produced. This will take more than seven years.
The mature queen is a gross, egg-laying machine (Figure 3). She measures about 1" in length, 1/4" in diameter. She weighs more than 100 times her original weight. She appears unusual or gross because all of the growth is in the abdomen. This produces a strange looking insect with a huge abdomen attached to a tiny head, thorax, and legs. Her abdomen is so large that her legs can no longer carry her. Since she cannot move, she must be fed, groomed, and moved by the workers.
All of the queen's increase in size and weight is due to the growth of her ovaries. She can now lay about 2000 eggs a day. She will live in a special queen's chamber for the rest of her life, if the colony is not disturbed.
The king's abdomen will also enlarge, although not as much as the queen's. He produces the sperm needed to fertilize the number of eggs laid by the queen. The royal pair may live 20 or more years.
As the colony grows, specialized castes are produced for the different tasks required. The first caste produced are the workers (Fiqure 4). These are small, white, blind, and quick-moving. They perform all the tasks required to maintain a colony. They forage for food, feed the king, queen, soldiers, and young, take care of the eggs, maintain the nursery, build tunnels and carton nests, open and close the flight slits for swarming, and bury or cannibalize abnormal or injured colony members. They are very susceptible to drying, so they work within tunnels and galleries. The workers can live for four or more years. They are responsible for all of the damage caused by termites. The great majority of individuals in a colony are workers.
The second caste produced are the soldiers. They have hard, brown heads with jaws that look like pincers (Figure 4). These jaws are strictly for fighting and are so specialized that they cannot be used to chew food, so the soldiers also must be fed by the workers.
The soldiers' job is to defend the colony against all enemies. Whenever there is a break in the tunnel, an internal alarm is triggered, which summons the soldiers to the break. The soldiers congregate around the break and bite any invader that tries to enter. When they bite, the soldiers can also eject a white latex-like liquid through a pore on the top of their heads. This sticky material can hinder the movement of enemies. The soldiers will stay in the exposed area until the workers repair the break. They will also fan out and protect the area until around open flight slits when the swarmers leave the nest.
The third caste to appear are the reproductives. Two types, primary and supplementary, are produced in a Formosan subterranean termite colony. The two types have different functions. Primary reproductives swarm and start new colonies. They are called alates or swarmers (Figure 5). They are brown, and they have wings and functional eyes. The skin of the primary is thick so the termites can swarm and survive in a dry environment for many days
Although thousands of primary reproductives are produced each year, they all leave the nest. Primaries can not become reproductive if they remain in their colony of origin. In a Formosan colony, the only primaries that reproduce are the original king and queen that started the colony.
Supplementary reproductives, on the other hand, can become reproductive only in the colonies in which they were born. Supplementaries are wingless, blind, and lighter in color than the primaries. They never leave the colony. They take over reproduction when the primary king or queen dies or becomes seperated from the main colony. It takes many supplementaries to equal the productivity of a pair of promaries.
The existence of these supplementaries in Formosan colonies is one of the many reasons for the difficulty in controlling this pest. Although control measures, such as treating the soil with insecticides, may cut off the part of the colony attcking a house from the reproductives on the ground, it does not neccesarily mean that the infestation in the house will not die out. Supplementaries can take over the reproductive function for the termites in the house. The latter will usually be able to find a source of moisture, and the infestation will continue with what then becomes an aerial colony.
Moreover, since the workers can live a long time, they can still cause significant damage before they die, even if there is no reproduction. With the Formosan subterranean termite, therefore, it is not enough just to cut the colony off from the ground and hope that the infestation in the house dies out. The infestation in the house must be treated.
Prevention and control of infestations of this termite require a careful, concerted attack. Here are a few simple things the homeowner can do to reduce the problem.
Management of this pest is predicated on breaking the food-moisture-niche triad. Removing any one of these elements will stop this morining.
Figure 1. Flight slits in a wooden beam.
Figue 2. Wingless female and male adults in tandem.
Figure 3. A mature Formosan subterranean termite queen.
Figure 4. Formosan subterranean termite soldier (left) and worker.
Figure 5. Winged adult swarmers (alates).
Reference to a company or product does not imply approval or recommendation of the product by the College of Tropical Agriculture and Human Resources. University of Hawaii, or by the United States Department of Agriculture to the exclusion of others that may be suitable.