What Do Termites and Mothballs Have in Common?
Formosan termites may not worry about moth holes in their sweaters, but they are the first insects discovered to fumigate their nests with naphthalene. Scientists have discovered that termites, like the Formosan Subterranean Termite (Coptotermes formosanus), produce naphthalene – a hydrocarbon – which they apparently use as a defense against natural enemies, such as ants.
People use the compound to rid human nests of carpet beetles and clothes moths and to repel intruders, such as bats and starlings. It also has antiseptic properties. However, naphthalene does not seem to bother Formosan termites, says urban entomologist Gregg Henderson, Ph.D., and his postdoctoral researcher Jian Chen of Louisiana State University Agricultural Center in Baton Rouge. In fact, they introduce the chemical as they construct their nests. And the Agricultural Center researchers have developed a method for using these unique gases to indicate the presence of termites.
A termite nest is a closed system which protects the termites in a microclimate that is controlled and different from that of the surrounding environment, Henderson says. As a soil-dwelling creature, Henderson notes, the termites confront many adversaries such as ants, fungus, bacteria, and nematodes. He believes that fumigating the nest with naphthalene and other volatile compounds may play an important role in inhibiting microorganisms and invertebrate invaders in the nest.
Henderson and his postdoctoral researcher, Jian Chen, found this unusual chemical in termite nests collected from colonies infesting houses and trees in New Orleans and Lake Charles, Louisiana. But the source of the naphthalene remains a mystery. Although Henderson admits that it may be possible for some animals to make naphthalene, he points out that there is no direct evidence of naphthalene being made by any animal or microorganism. Since termites use soil, masticated wood, and excrement to make their nests, one possible source is in the processed food of the termites or the soil, Henderson speculates. Another possible origin, he says, is that microbes are making the naphthalene by acting on material in the termite nest, the gut, or on the food.
Jian Chen from Louisiana State University and colleagues discovered that the termites incorporate naphthalene in their underground nests, which they build by cementing together soil and masticated wood with their saliva and excrement. In every kilogram of nest material, there was between 50 and 200 micrograms of naphthalene.
At these concentrations, the researchers demonstrated that Red Fire Ants (Solenopsis invicta), one of the termite’s main predators, become paralysed, and that fungal growth is inhibited; but even at these concentration levels, the gas had no visible effect on the termites.
As a fumigant, naphthalene is ideal for termite nests, vaporising easily to permeate the complex system of tunnels. But naphthalene may not be limited to defence. The researchers also showed that soldier termites follow trails of dilute naphthalene, indicating a possible use in the coordination of colony behaviour.
The presence of naphthalene in C. formosanus nests is quite remarkable. Tar, coal, petroleum, and the products of partial combustion of organic matter, were once thought to be the only sources of naphthalene in nature. These termite nests now join magnolia flowers and the forehead of male White-tailed Deer (Odocoileus virginianus) as unusual places for naphthalene to be found. Exactly how the termites obtain naphthalene, or whether they manufacture it themselves, is unknown.
Chen, J., Henderson, G., Grimm, C.C., Lloyd, S.W. & Laine, R.A., 1998. Termites fumigate their nests with naphthalene. Nature 392: 558--559.
Researchers Develop Termite Detection System That May Hold Answer to Combating Formosan Termites
One day a typical home may include a termite detector in addition to the customary smoke detectors and carbon monoxide detectors. And that day could be soon – once a new termite detection system developed by the Louisiana State University Agricultural Center in Baton Rouge is perfected and on the market.
A product of the combined efforts of Dr. Gregg Henderson and Dr. Jian Chen of the Agricultural Center's Department of Entomology and Dr. Roger Laine of its Department of Biochemistry, the system has the potential to save homeowners millions of dollars a year by early detection of the wood-eating pests.
"Most termite inspections start with a technician in an attic or basement with a flashlight and a screwdriver or knife, poking at rafters and floor joists, looking for damage caused by termites," Henderson says. "By that time, a lot of damage may have been done."
They've discovered that termites produce naphthalene – a hydrocarbon they apparently use as a defence against natural enemies, such as ants. And the researchers developed a method of using these unique gases to indicate the presence of termites.
The detection system, which has a patent pending, samples the air in the walls of a building and analyzes its composition. If the system identifies the chemicals associated with termites, there's a strong possibility the insects are there, the experts say. A homeowner's inability to detect the presence of termites before their activities become noticeable is a major obstacle in early termite control.
"It's our weakest link in fighting termites," Henderson says. "Currently, termites are found through indirect methods after they've already done significant damage."
A historic 150-year-old cotton warehouse on New Orleans' riverfront near the Garden District is the site of a full-scale field test of a new patented bait system that holds the promise of controlling dreaded Formosan subterranean termites.
Dr. Gregg Henderson and Dr. Jian Chen developed the bait system that lures termites into a feeding chamber and then entices them into a second chamber that contains toxin-laced material, which the invaders carry back to their nest to kill the entire colony.
Developed with funds from the LSU Ag Center, the apparatus is made from a plastic cylinder about 8 inches long and 4 inches in diameter. It's divided into two chambers by a wall with a small hole in the center. The first chamber contains a small amount of cardboard as an introductory food source for the insects and a paper plug that initially keeps termites out of the other section, Henderson explains.
Because they don't know how easily a termite colony would find them on its own, the researchers "pre-conditioned" the bait stations by placing termites in the non-toxic sections before they set them out. Henderson's crew placed about 30 of the devices around the warehouse near the mud-walled shelter tubes that the targeted termites build and use for travel between their colony and food sources.
"Putting the apparatus near a shelter tube is easier than trying to find the actual colony site, which may be deep beneath the ground or, in the case of Formosan termites, hidden behind building walls," the entomologist says. After these introduced termites feed on the cardboard, they should venture into nearby shelter tubes and lay down trails that termites in the targeted colony will follow back to the bait.
The trail that leads into the bait station is important too.
"Termites make and follow chemical trails to and from their nests to find their way back again," Henderson says. "We hope we can take advantage of that to lure them to the toxicant."
Eventually, the termites will consume the cardboard and then the plug between the two chambers of the bait system, opening up the second side containing the insecticide-laced bait.
"We use two chambers to make sure the termites blaze a trail to the colony and back again before they consume the toxicant," Henderson explains. The termites that eat the pesticide-laced paper will take the chemical back and feed others. Eventually, they'll all die as the toxicant is distributed throughout the colony.
"The toxicant is a chitin inhibitor that affects the molting process of the termites, but it doesn't harm people because we don't have chitin, nor do we molt," Henderson says. "The paper bait is being manufactured and provided by Ensystex, the newest bait on the market."
Termite baits are slow-acting and may take about six months to effectively eliminate a problem, Henderson says. A cellulose-containing monitor can be used to measure consumption and termite activity and evaluate control. Within six months from the start of the New Orleans study, Henderson expects to show significant control.
A termite colony can have a population from 500,000 to as many as 10 million, he explains. A quarter million termites can be killed with as little as 0.01 grams of active ingredient when it is provided in a bait formulation. "We can't really prove the elimination of termites, only the lack of activity," Henderson says, "We may never be able to eliminate a colony, only knock it back and control it so it won't cause problems."
About Formosan Termites
Formosan termites are the most aggressive and destructive timber pests in the United States. It is an imported species native to China. It can develop huge nests containing millions of termites aggressively and relentlessly seeking and devouring structural timbers, utility poles and other timber structures, including ships and barges. Infestation can occur to living trees, such as oak, cypress, pine and maple. They often cause power failures by chewing through electrical cabling. A termite to be feared, it is known to cause major structural timber damage to homes and buildings within a few months.
The Formosan subterranean termite (Coptotermes formosanus) has now become established in Florida and other southern states. At least one colony has been found In California (1995). Formosan termites are a serious timber pest in Hawaii and coastal regions of Texas, Florida, Louisiana, Mississippi, Alabama, Tennessee, Georgia, South Carolina and southern California, as well as inland towns and cities. The Formosan termite is rarely found North of 35° N latitude. They have been reported from 11 states, including Alabama, California, Florida, Georgia, Hawaii, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, and Texas. Their distribution will probably continue to be restricted to southern areas because their eggs will not hatch below about 20° C (68° F).
Formosan termites swarm in huge numbers in late spring or summer, usually following a warm rainy day. They prefer to swarm in times of high humidity in the evening hours from dusk to midnight. The swarmers are attracted to lights and are about 1/25'', including wings. Their body color is pale yellowish brown. A fontanelle (frontal gland pore) is present. The swarmers have four wings of equal size with dark hard veins in the front portion of the front wing. The wings are a translucent, slightly milky color and covered with tiny hairs.
The armoured head of the soldier is rounded, tapering toward the front. A fontanelle (frontal gland pore) is present on the soldier's forehead. They have large mandibles relative to their body, which is flat and narrower than the head. When disturbed, the Formosan soldier termite may emit a white sticky latex substance from its fontanelle – a defensive measure to ensnare their enemies, primarily ants.
Formosan termites eat mainly the springwood of susceptible timbers, most often leaving the summer wood sections. Timbers infested by Formosan termites usually have layered sections packed with moist soil in high-activity areas. Formosan termites are subterranean termites that typically live in the ground, and a large mature nest will periodically emit swarmers in large numbers over a wide area to find a mate from another colony nest to start up a new colony.
A suitable location for nesting should provide a constant moisture source and a readily available timber food source close by. Several years are required before the termite colony reaches the typically mature size, which may contain millions of termites foraging for timber food sources within a 400 feet radius, actively feeding on trees and free-standing poles as well as buildings and other timber structures.
The colony nests of Formosan termites are usually located in the ground below the frost line but above the water table. They typically construct mud galleries or "shelter tubes" across hard objects in order to gain access to timber food sources. Formosan termites constantly search for new food sources. They are known to enter buildings through cracks in concrete flooring or to travel under parquetry or tile flooring through gaps of less than 1/16" wide. The space between the foundation and the first mortar joint is often enough space for termites to enter a home.
Formosan termites can establish secondary colonies in very moist wood of upper stories of buildings (even several stories above ground) and do not need soil contact if there is a nearly constant moisture source. Where moisture regularly collects inside the wall or other cavities of a building, say from faulty plumbing or broken roof tiles, the Formosan termite can develop a subsidiary colony nest, which may not require contact with the ground to ensure its survival. This is particularly prevalent in areas of high humidity where wood moisture is above average. Due to its size and aggressive foraging behaviour a colony of Formosan termites does more damage than single colonies of other US subterranean species and can cause significant structural damage to a home within six months.
Study on Termite Bacteria May Aid In Greenhouse Gas Understanding
Most people would rather see wood-eating termites completely exterminated. However, these insects' digestive processes, which prove so maddening to homeowners, may provide insight into why some animals produce more greenhouse gasses than others, said a University of Iowa researcher.
Jared Leadbetter, Ph.D., a UI postdoctoral associate of microbiology, has built upon earlier studies that found wood-feeding termites digest their fiber-rich food in a highly productive manner and, consequently, emit less methane into the atmosphere than expected.
Methane is a potent greenhouse gas and a major contributor to global warming, according to the U.S. Environmental Protection Agency (EPA). In comparison to termites, cattle, which also have a diet rich in fiber, are less efficient. As much as 20 percent of the energy contained in the grass that cows chew is later emitted into the atmosphere as methane. Scientists do not understand which factors lead to these two very different outcomes.
Learning more about termites could lead to improvements in cattle nutrition and decreases in their methane emissions, Leadbetter said. As a contributor to global warming, methane is second only to carbon dioxide, according to the EPA. Over the last 200 years, methane concentrations have more than doubled, largely due to human-related activities. Livestock are among the largest sources of methane from human-related activities. The roughly 100 million cattle in the United States produce about six million metric tons of methane into the atmosphere annually, the EPA found.
In the article that appears in Science, Leadbetter and his colleagues investigated bacteria known as spirochetes that are found in termites' guts. Leadbetter and his colleagues conducted the research at Michigan State University, where Leadbetter pursued his doctoral and post-doctoral studies. Leadbetter came to the UI in June 1998. The scientists found that these spirochetes consume hydrogen, a key intermediate produced during the digestion of plant fiber. The spirochetes nourish the termites by converting the hydrogen into acetate -- an excellent food source for both termites and cows.
In cows, the spirochetes apparently are absent or unable to convert the hydrogen into acetate because such hydrogen is converted into methane. "Comparing them mouthful to mouthful, the termite is more efficient than the cow," Leadbetter said. "These spirochetes help to explain this. By conducting basic science, we have learned things about the termite that may have productive applications down the road.
For instance, other researchers might be stimulated by our results to find novel ways to improve the nutrition of cattle." Leadbetter also noted that the spirochetes' beneficial role in termites contrasts with the notorious roles of other spirochetes as "germs" causing syphilis and Lyme disease. By performing studies on diverse subjects such as the termite gut, scientists hope to continue to discover new microbes that carry out previously unappreciated but beneficial roles in nature.