TERMITES

Termites, sometimes incorrectly called "white ants", are a group of social insects usually classified at the taxonomic rank of order Isoptera.  Termites mostly feed on dead plant material, generally in the form of wood, leaf litter, soil, or animal dung, and about 10% of the estimated 4,000 species (about 2,600 taxonomically known) are economically significant as pests that can cause serious structural damage to buildings, crops or plantation forests. Termites are major detrivores, particularly in the subtropical and tropical regions, and their recycling of wood and other plant matter is of considerable ecological importance.

As social insects, termites live in colonies that, at maturity, number from several hundred to several million individuals. They are a prime example of decentralised, self-organised systems using swarm intelligence and use this cooperation to exploit food sources and environments that could not be available to any single insect acting alone. A typical colony contains nymphs (semi-mature young), workers, soldiers, and reproductive individuals of both genders, sometimes containing several egg-laying queens.

SUBTERRANEAN TERMITES

Subterranean termites are the most destructive insect pests of wood in the United States. They cause more than $2 billion in damage each year, more property damage than that caused by fire and windstorm combined.

In nature, subterranean termites are beneficial. They break down many dead trees and other wood materials that would otherwise accumulate. The biomass of this breakdown process is recycled to the soil as humus.

Problems occur when termites attack the wooden elements of human structures -- homes, businesses and warehouses. Their presence is not readily noticed because they hide their activity behind wallboards, siding or wood trim.

Homeowners in all areas of of the nation should watch for subterranean termites and take precautions to prevent infestations. To minimize damage from termites, it is helpful to know the description, life cycle and infestation signs of termites as well as preventive and control measures.





Distribution
Several species of subterranean termites are found in the United States; they live in every state except Alaska Two major types in Texas are the most common termite pests that seriously threaten wooden structures: 


Identification
Subterranean termites are social insects that live in nests or colonies in the soil, hence their name “subterranean.” These colonies contain three forms or castes: reproductives, workers and soldiers. Individuals of each caste have several stages: the egg; the larva that develops into a pseudergate and eventually into a brachypterous nymph or soldier; and the adult. Reproductive adults have three forms: primary, secondary and tertiary reproductive.

Reproductive males and females can be winged (primary) or wingless (secondary or tertiary). Each can produce new offspring. The bodies of primary reproductives, also called swarmers or alates, vary by species from coal black to pale yellow-brown. Wings may be pale or smoky gray to brown and have few distinct veins. Swarmer termites are about 1/4 to 3/8 inch long.

Secondary and tertiary reproductives in the colony are generally white to cream-colored and may have short wing buds. Developed as needed, they replace a primary queen when she is injured or dies. They also develop in addition to the primary queen and lay eggs for the colony. Supplementary reproductives, including a group of males, workers and soldiers, may become isolated from the main colony and can establish a new colony.

Termite workers make up the largest number of individuals within a colony. Workers are wingless, white to creamy white, and 1/4 to 3/8 inch long. They do all of the work of the colony -- feeding the other castes, grooming the queen, excavating the nest and making tunnels. In working, they chew and eat wood, causing the destruction that makes termites economically important.

Soldiers resemble workers in color and general appearance, except that soldiers have large, well-developed brownish heads with strong mandibles or jaws. Soldiers defend the colony against invaders, primarily ants. In some types of termites generally occurring in arid regions, soldiers are called nasutes. Nasute soldiers have pear-shaped heads with a long, tube-like projection on the front. They exude a sticky substance to entrap their enemies.

It is important to be able to distinguish between swarming termites and ants. They often swarm around the same time of year, but control measures for each differ greatly.


Biology and habits
After a termite colony matures, which requires from 2 to 4 years, swarmers are produced. Swarming usually occurs from January through April, during the daylight hours, usually after a rain. Environmental factors such as heat, light and moisture trigger the emergence of swarmers. Each species has a definite set of conditions under which it swarms. The number of swarmers produced is proportionate to the age and size of the colony.

Both male and female swarmers fly from the colony and travel varying distances. They are extremely weak fliers; wind currents usually carry those that travel any distance. Only a small percentage of swarmers survive to develop colonies; the majority fall prey to birds, toads, insects and other predators. Many also die from dehydration or injury.

A pair that survives lands and immediately seeks cover under rocks or other materials. The pair makes a very small nest before mating. Initially, the new queen termite lays only a few eggs. The male, or king, remains with the female because periodic mating is required for continued egg development.

Eggs are not deposited continuously; in fact, only a few hundred are deposited during the first year. In subsequent years, the young queen grows larger and lays more eggs. Larvae hatch from the eggs within several weeks and are cared for by the new king and queen. The larvae molt into pseudergate workers, and then into presoldiers or brachypterous nymphs. The colony stabilizes when the queen reaches maximum egg production. If the queen dies, secondary reproductives take over the queen’s duties.

The maximum size of a colony depends on such factors as location, food availability and environmental conditions, especially temperature and moisture. Some colonies remain small; others contain up to several thousand individuals.

New colonies form when the old colony produces swarmers or when groups of termites become isolated from the main colony and establish subcolonies. This is called colony splitting. These subcolonies may exist independently or unite with the main colony.

Subterranean termites derive their nutrition from wood and other material containing cellulose. Paper, cotton, burlap or other plant products often are actively attacked and consumed by termites. Subterranean termites cannot digest cellulose directly. They depend on large numbers of one-celled animals (protists) living in the termite hind gut to break down the cellulose to simple acetic acid, which termites can digest. Worker termites and older nymphs consume wood and share their nourishment with the developing young, other workers, soldiers and reproductives.

Termites are very attracted to odors of wood-decaying fungi that, through the decay process, make the wood easier to penetrate. In some instances, the fungi provide a source of nitrogen in the termite diet.

Moisture is important to subterranean termites, which have very little resistance to dehydration. To survive, they must maintain contact with the soil (their primary moisture source) or other above-ground moisture sources, such as in structures with defective plumbing or guttering.

Subterranean termites also must protect themselves from temperature extremes and attack by such natural enemies as ants and other insects. Termites foraging for food above ground protect themselves with shelter tubes, which are sometimes called mud tubes. Worker termites build the tubes from particles of soil or wood and bits of debris held together by salivary secretions. The tubes may be thinly constructed or large and thick-walled to accommodate many termites moving vertically between the soil and the food source.

This construction material also is found lining the galleries built in wood being attacked and aids in identifying termite-damaged wood. Shelter tubes often are used to bridge masonry or other objects, allowing termites access to a food source (wood) above ground.


Damage
Dead trees and brush are the original food source of subterranean termites. When land is cleared of this material and houses are built on these sites, termites attack the structures. Termites can enter buildings through wood in direct contact with the soil, by building shelter tubes over or through foundations, or by entering directly through cracks or joints in and under foundations.

Any material in direct contact with the soil -- such as trees, vines or plumbing fixtures -- serves as an avenue of infestation. Subterranean termite swarmers may also be blown into or on structures and then start a new colony.

In nature, termites function as decomposers that breakdown dead wood that accumulates in and on the soil. The beneficial products of this breakdown process are returned to the soil as humus. Drywood and subterranean termites are the most destructive insect pests of wood, causing more than $1.7 billion in damages and cost of control each year in the U.S. alone. Their presence in structures is seldom noticed until damage is discovered or the termites swarm within the building.

Drywood termites are found in the southern tier of states, from North Carolina through the Gulf Coast and into the coastal areas of California.

General Biology

Drywood termites are social insects that live in colonies in sound, dry wood. Each colony consists of offspring from an original pair (male and female). There are three growth stages – eggs, immatures and adults. Drywood termites are larger than local, southwestern subterranean species.

In comparison to other termites drywood colonies are rather small (a few thousand individuals), and the colony develops relatively slowly. They neither live in the ground nor maintain contact with the soil, and they do not build mud tubes.

Subterranean termites produce liquid feces, whereas drywood termites produce characteristic pellets. These pellets are eliminated from the galleries through “kick holes”. Pellets tend to accumulate on surfaces located below the kick holes and are usually the first evidence of a drywood termite infestation.

Drywood termites tend to cut across wood grain destroying both the soft spring wood and the harder summer growth. Subterranean termites typically follow the grain of the wood, feeding primarily on the soft spring wood.

The reproductives are winged (alates or swarmers) or wingless males and females that produce offspring. The primary reproductives, also called swarmers or alates, vary in body color from dark brown to light yellowish tan. Their wings may be almost clear to smoke gray, and have few distinct veins in them. Swarmer drywood termites are about 7/16 inch long, including the wings. If the primary reproductives die, they are replaced by immatures that can become capable of reproductive activity. They are known as replacement or secondary reproductives.


In most drywood species there is no true worker caste (subterranean termites do have a true worker cast); this function is taken over by immatures. These immatures are wingless, white to beige in color, 1/4 to 3/8 inch long and make up the largest number of individuals within a colony. They gather food, enlarge the nest and feed and care for the queen, younger immature forms and others in the colony.

Soldiers resemble immatures in color and general appearance. However, they have large, brownish to yellowish-brown heads with enlarged, heavily sclerotized mandibles (jaws). Soldiers defend the colony against invaders, primarily ants. Soldiers are about 5/16 inch long.

After a drywood termite colony has matured (several years), winged alates (swarmers) are produced that leave the colony to establish new colonies. Swarming activity (nuptial flights) generally occurs at dusk or during the night and they tend to fly towards areas of greatest light intensity, gathering around lights or illuminated windows. However, the dark western drywood termite (Incisitermes minor) is a daytime swarmer. Swarming of Arizona species occurs in early to late summer with certain species swarming during the winter months of January and February also.

Some termite species are very regular down to the time and day of year that nuptial flights are made. Other species vary widely on the day and time. Certain environmental conditions, such as heat, light (time of day), rainfall and moisture conditions, wind, atmospheric pressure (especially rapid changes in pressure) and the electrical properties of the atmosphere (associated with thunderstorms) trigger the emergence of alates, and each species has a definite set of conditions under which swarming will occur. The number of alates produced will be proportionate to the age and size of the colony, while environmental conditions regulate the number of swarms emerging from the colony. The bulk of a colonies alates will be released in one or two synchronized swarms, then a few at a time are released throughout the rest of the season. Swarming constitutes a dispersal stage, rather than a true mating flight.

Male and female alates fly from the colony and travel varying distances. They are extremely weak flyers, but individuals can travel great distances carried by air currents during the summer monsoon season. Any alates that try to return from the outside are usually killed. Often, the soldier castes congregate around colony openings to defend the release of the alates.

Only a small number of the swarmers survive to develop colonies. The majority fall prey to birds, toads, reptiles, insects (primarily ants) and other predators. Many others die from dehydration or injury. When a pair alights, they shed or pull off their wings and immediately attempt to enter wood. Swarmers usually enter wood through cracks, natural checks, overlapping or adjoining pieces, or exposed end grain. A very small nest is developed after the pair has mated. Initially the queen lays relatively few eggs. The male, or king, remains with the female, since periodic mating is required for continued egg development.

Immatures hatch within several weeks and are cared for by the king and queen. After two molts, immatures assume the role of workers and begin to feed and care for the original pair. Eggs are not deposited continuously, and in fact, very few are deposited the first year. In subsequent years, the young queen matures and will lay more eggs. Eventually, the colony stabilizes when the queen reaches maximum egg production. At that point the colony will contain eggs, immatures, soldiers and reproductives. If the queen dies, one or more secondary reproductives take over her duties. The maximum size of a colony depends on factors such as location, food availability and environmental conditions. Most colonies remain small, but multiple colonies in the same piece of wood may contain up to 10,000 individuals. A colony grows through the queen’s increased egg production and the accumulation of long-lived individuals.

Drywood termites derive their nutrition from cellulose in wood. Within the termite’s gut are large numbers of bacteria and single-celled animals called protozoa. The protozoa produce enzymes that digest cellulose causing the break down of wood particles to simpler compounds that termites can absorb as food. The immatures consume wood and share their nourishment with the developing young, soldiers and reproductives.

Moisture is not as important to drywood termites as it is to subterranean termites. Drywood termites require no contact with the soil or with any other source of moisture. They extract water from the wood on which they feed, and also produce water internally during the digestive process. They require as little as 2.5 to 3 percent moisture, but prefer wood with 10 percent moisture content. Drywood termites often establish nests in roof materials and wooden wall supports accessed under eaves. However, despite being capable of surviving on low wood moisture they are also found in wood associated with a water source such as a leaky pipe or water heater. Dead wood accumulating around buildings and homes often serves as a source of infestation.

Homeowners most commonly confuse winged ants with termite alates as several species of ants and termites swarm during the same season.Adult Incisitermes minor swarm during the daylight hours usually during the months of May through early August in Arizona. They fly into attics accessible areas of poorly vented houses. A favorite place for entry is in the crack created by drying plaster or stucco as it pulls away from window and door frames. It is necessary for most termites to be able to get a purchase on the wood that it intends to invade. Normally, termites will not just land on wood tunnel effectively. However, if they can crawl down into cracks and crevices, their chances of tunneling successfully are greatly increased.

Dark western drywood termite swarmers are about 7/16-1/2 in (11-12.5 mm) long, including wings, which are 3/8 in (8.5 mm) or longer. Alates of the dark western drywood termites have an orange brown head and pronotum (first segment of the thorax, behind the head), the abdomen is dark brown, wing membranes and pigmented veins are blackish. The soldiers have orange to reddish brown heads with whitish eyespots. The head slopes down gradually from the top which is flattened to slightly rounded on side view; the antennae have a 3rd segment which is enlarged and club-like; the pronotum is as wide or wider than the head when viewed from the top.

(Marginitermes hubbardi) is found in the Sonoran desert areas of California and Arizona. It is also referred to as the southern drywood termite. This termite has very similar habits to the dark western drywood termite, but can tolerate drier conditions and higher temperatures.

Alates of the light western drywood termite are pale in color. Soldiers have a club-like third antennal segment that is almost as long as all the succeeding segments combined. This characteristic makes the species easy to distinguish from others.

The reproductives are a uniform light chestnut brown in color, and about 7 to 8 mm in length without wings. This species swarms at dusk May through early September.

Damage

Dead trees, branches, brush and firewood from residential areas are the primary habitat of drywood termites. When land is cleared and houses or other buildings constructed, these structures are then subject to attack. Drywood termites enter structures through attic or foundation vents, directly through or under wood shingles, under eaves and fascia boards, and through natural cracks, checks and joints in exposed wood trim, window and door frames and sills. Drywood termite alates can penetrate flat wood surfaces, but prefer to wedge themselves into narrow places to begin tunneling. Most new homes are constructed on concrete slabs and have tile roofs. However, attic areas are normally vented and wood trim is still commonly used externally.

Signs of Infestation

Generally, the first indirect sign of infestation is the discovery of fecal pellets or the presence of alates on windowsills or near lights. Alates found inside the house (if windows and doors have been closed), are an indication of infestation within the structure. Another indication of infestation is the presence of discarded wings near emergence sites, on windowsills or caught up in cobwebs. The presence of alates outdoors is a natural phenomenon and is not an implication of home infestation.

Drywood termites spend their entire lives inside wood. They construct round “kick holes” in infested wood, through which the fecal pellets are eliminated from the galleries or tunnels. These pellets accumulate in small piles below the kick holes, or will be scattered if the distance between the kick hole and the surface below is very great. Fecal pellets also may be found caught in spider webs.

Fecal pellets are distinctive and used for identification of drywood termite infestation. Drywood fecal pellets are hard, elongated and less than 1/25 inch long. They have rounded ends and six flattened or concavely depressed sides with ridges at angles between the six surfaces. The characteristic shape results when the termite exerts pressure on the fecal material to extract and conserve moisture in its hindgut. Typically the pellets are a light tan in color with some black ones mixed in.


Characteristics of Damaged Wood

Wood, which has a dull or hollow sound when tapped, should be examined closely. Careful probing of wood with a sharp instrument may disclose drywood termite galleries. The interior of infested wood contains chambers connected by galleries or tunnels that cut across the wood grain. The galleries have a smooth, sculptured appearance and contain few if any fecal pellets. Accumulations of pellets sometimes may be found in blind galleries or unused tunnels.

Control

Control measures include reducing the potential for drywood termite infestations, preventing termite entry, removal of infested wood and applying chemicals or other remedial treatment.