Subterranean Termites

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Subterranean Termites

  • Post category:Termites Control
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Subterranean Termites:

General Description

Several records pertaining to termites in the Arab Gulf countries, especially in Saudi Arabia, were made. The termite fauna of the Arabian Peninsula comprises 22 species. In the UAE, three research projects were conducted and published by Prof. Walid Kaakeh (2005 and 2006) and revealed the discovery of eight (8) species of subterranean termites:

Species, common name (if any) Family
Heterotermes aethiopicus (Sjostedt), NCN Heterotermitidae
Amitermes vilis (Hagen), NCN Termitidae
Anacanthotermes ochraceus (Burmeister), Harvester termite Rhinotermitidae
i.      Anacanthotermes ubachi (Navas), Harvester Termite Rhinotermitidae
ii.      Psammotermes hypostoma Desneux, Sand termite Rhinotermitidae
iii.      Microcerotermes diversus (Silvestri), Small waxy termite Rhinotermitidae
iv.      Microtermes najdensis (Harris), NCN Rhinotermitidae
Odontotermes smeathmani (Fuller), NCN Termitidae

NCN = No Common Name

The most common subterranean termites are Heterotermes aethiopicus and Amitermes vilis:

Heterotermes aethiopicus (Sjostedt)

   

Amitermes vilis (Hagen)

 

Life Cycle and Common Characteristics

  • Termites are social insects (i.e., there is a division of labor between different types of individuals or castes).
  • Nearly all termite species have reproductive and soldier castes.

Caste system of termites:  A – King, B – Queen, C – Secondary queen,

D – Tertiary queen, E – Soldiers, F – Worker.

  • In many termite societies, there is also a distinct worker caste, but in most of the more primitive species, the typical duties of the worker nymphs are food gathering, feeding reproductives and soldiers, and nest building.
  • Even in species with workers, the older nymphs usually do much of the work.
  • Workers and nymphs of subterranean termites perform all the work of the colony and are the ones who do all the damage to structures.
  • Soldiers serve only to defend the colony against enemies. They cannot eat wood.
  • Workers feed soldiers, together with the reproductive organs.
  • Both workers and soldiers are blind.
  • Winged adults are referred to as the primary reproductives (often called swarmers). They leave the colonies on colonizing flights at certain times of the year. After these flights, a male (the king) and female (the queen) will pair up, lose their wings, construct a small cell in the soil, mate, and the queen will lay eggs.
  • In colonies where these primary forms are no longer present, supplemental or secondary reproductives without pigmentation or functional wings occur, often in large numbers. Each colony supports itself and has no contact with other colonies.
  • In nature, termites help convert dead wood and other organic materials containing cellulose to humus. From this standpoint, termites are very beneficial animals. Only when people began building with wood in the natural home of the termites did they start feeding on buildings.
  • Termites harbor one-celled organisms in their digestive tracts, and these organisms convert cellulose into substances the termites can digest.

Termite Social Castes

  • The stages in the life history of subterranean termites are essentially the same for various species. Termites develop via gradual metamorphosis from eggs, which are laid by the primary or secondary reproductives.
  • Nymphs hatch from the eggs and undergo several molts, through which different individuals develop into one of the various castes.
  • Four different castes can develop from nymphs: workers, soldiers, winged primary reproductives, and supplementary reproductives.

  • In new colonies, nymphs from the first small batch of eggs usually all become workers. Other forms not normally produced until later egg laying. In the species where a distinct worker cast occurs, workers are the most numerous individuals in a termite colony.
  • In new colonies, nymphs from the first small batch of eggs usually all become workers. Other forms are normally not produced until later in the egg laying cycle.In the species where a distinct worker cast occurs, workers are the most numerous individuals in a termite colony.

  • Worker termites perform all of the work of the colony, feeding the other caste, grooming the queen, excavating the nest, and making the tunnels. In the process of making nests and tunnels and ingesting food, they chew and eat wood, thus causing destruction, which makes termites economically important. The workers are usually light-colored and do not have wings or any specialized structures.

  • Soldier termites serve specifically to protect the colony from its enemies. Their heads are quite hard and they have much larger jaws than those found in the other forms. When openings are made into termite workings, the soldiers gather with their large heads and strong mandibles facing outward and protect the colony from invaders.
  • Supplementary reproductives:
  • Both sexes of the reproductives are wingless or have only very short, non-functional wings.
  • They are developed as needed and quickly replace a primary queen who is injured or dies.
  • They usually develop in addition to the primary queen and become the most important source of eggs in the colony.
  • When supplementary reproductives, with a group of males and workers, become isolated from the main colony, they can establish a new colony, thus spreading the original infestation without being visible above ground at any time.

  • Primary reproductives (swarmer termites):
  • They are often seen by homeowners.
  • Winged adults are usually much darker than the other members of the colony.
  • All four wings are the same length and extend beyond the tip of the abdomen by more than the length of the body.
  • Both male and female reproductives leave the colony in great numbers (swarms), usually in the spring or fall. These swarms are often the first visible indication that termites are present.
  • The environment’s conditions must be just right before termites swarm.
  • The temperature, moisture both inside and outside the colony, light conditions, and even barometric pressure influence swarming activities. Swarmers emerge on warm, sunny days when the humidity is high (e.g., often on days following rain showers).
  • After a brief flight, the wings are broken off, and males and females pair up and attempt to establish a new colony.
  • The supplementary reproductives are responsible for the production of most of the eggs within a colony after it has become established.

Termite Ecology and Its Environment

  • Construction of Mud Tubes

Termite tubes are one of the first signs of a termite infestation. They construct tubes (called “mud tubes”) when they pass over exposed areas. Tubes serve to protect the termites from their enemies (especially ants), conceal the termites, provide them with a moist environment, and protect them from dry air.

In general, the termite tubes range from 3 to 25 mm in diameter. They can be easily noticed when present along walls and near the building foundation. Tubes also may be hidden in typically inaccessible places, such as inside walls, crawlspaces, cracks in the foundation, or behind baseboards.

Four types of mud tubes are constructed by subterranean termites and serve different purposes for the colony:

Exploratory Tubes:

  • Exploratory tubes are thin and fragile, easy to see because they branch out in multiple directions.
  • Exploratory tubes are thin and fragile, easy to see because they branch out in multiple directions.
  • They are made of feces, saliva, and dirt and can extend up to 15 feet above ground when built over concrete or metal.
  • Used to search for sources of food, exploratory mud tubes rise from the soil, but they do not connect to any wood.

 

  • Although the tubes are empty, they still indicate the presence of termites. The pests will have moved to other sections of the home to find accessible food.

 

Working Tubes or Utility Tubes:

  • Every day, hundreds to thousands of termites are transported from their nests to food sources via working tubes.
  • The tubes are organized like a highway, with some lanes used to carry food while the others are used for construction and repair.
  • These tubes typically measure between 0.5 and 2.5 cm in diameter.

 

  • These tubes are made to last longer than exploratory tubes.

  • These allow termites to travel long distances along basement walls and home foundations.
  • They may also be found around window and door frames.

 

Swarm Castle / Swarm Tubes:

  • Termite workers construct swarm castles to temporarily accommodate the numbers of termite swarmers leaving the colony during a swarm.
  • Swarm castles can be very large and delicate.

  • The location where swarmers gather before leaving the nest is smooth and free from debris. When the time is right, workers begin to direct swarmers to the protective castle, and the swarmer termites move through the numerous exit holes, take flight, and begin the process of establishing other colonies.

Drop Tubes

  • Drop tubes are suspended between the ground and wood members of the structure.
  • They’re easy to identify.
  • Their purpose is to make food sources more accessible to termite workers and to re-establish a connection with the ground and working tubes.

  • Drop tubes are lighter in color than exploratory or working tubes because they contain more wood fibers. However, they have a similar diameter and brittleness to exploratory mud tubes.

 

 

Communication in the colony

  • Communication is needed to maintain efficient social integration and the division of labor. The basic means of communication in termites are via:

1- Chemical (pheromone) communication:

  • Each colony develops its own characteristic odor.
  • Any intruder (a termite from another colony, an ant, or any other natural enemy) is immediately recognized as foreign when it enters the colony.
  • An alarm pheromone is always secreted by the colony that triggers soldier termites to attack and kill the intruder. If a hole in the termite workings occurs, it is immediately required by the workers.
  • When a foraging termite worker finds a source of food, it recruits others to the food source by laying a chemical (pheromone) trail. The more foragers that find the food and return with it to the colony, the more intense the pheromone trail becomes.  As the food source is depleted and the foragers no longer deposit the pheromone, the trail deteriorates and eventually is abandoned.

 2- Sound:

  • Termite soldiers and workers bang their heads rapidly on the surface of their mud tunnels or wood galleries when the colony is disturbed.
  • The vibration of the surrounding surface is perceived by others in the colony, and they too take up the banging activity. This activity, like the alarm pheromones mentioned earlier, serves to mobilize the colony’s defences.

3- Trophallaxis (the reciprocal exchange of nutrients and food between colony members):

  • Trophallaxis permits the efficient use of nutrients within the colony, enhances recognition of colony members, distributes chemicals involved in caste regulation, and transfers cellulose-digesting protozoans.
  • Termites exchange food from both the mouth and the hind gut. When termites shed their skin during molting, they also lose their hindgut contents, including the protozoa they need for digesting wood. To get a new supply of protozoa, they must feed from the hind guts of other colony members. The feeding of the queens and soldiers by the workers is also a form of trophallaxis.
  • The proportion of the castes in the colony is also regulated chemically. The soldiers and reproductives produce chemicals that are distributed to other colony members by trophallaxis. These chemicals inhibit the production of additional sperm and eggs. Termites may react to a high level of soldier-produced chemicals by killing some of the soldiers.
  • In most subterranean termite colonies, nymphs can molt into workers, soldiers, or reproductives; workers can change into soldiers, nymphs, or supplementary reproductives; and nymphs that have begun developing wing buds may actually lose them with additional molts and return to the worker stage. All these changes are chemically regulated within the colony, depending on its needs.

 

Feeding Damage and Economic Implications

  1. Food Preference and Wood Consumption

  • Subterranean termites have preferences in the type of wood they will eat. Although woods like cedar are less preferred by termites, no wood is completely immune to attack.
  • The condition of the wood is also important. Decayed wood is eaten faster and is preferred over sound wood. Termites working in the wood facilitate decay by increasing the moisture content. Thus, termite damage is usually associated with decaying wood.

  • Termites working in the wood facilitate decay by increasing the moisture content. Thus, termite damage is usually associated with decaying wood.
  • Depending on the subterranean termite species, a termite worker consumes wood at approximately the rate of 2 percent of their body weight each day.

 

  • Factors affecting the consumption rate include environmental conditions, termite size, and colony size. Also, some species are more destructive than others. A colony of one species containing one million workers may consume 5 grams of wood each day, while other species containing 400,000 workers may consume 30 grams of wood every day.
  • Although the quantity of wood being eaten is small over a short period of time, significant damage can be done over months of time.

  • The mud and moisture brought into a structure by termites exacerbates the damage. Thus, early detection and control of an infestation are desirable.

 

   

  1. Foraging Territory

  • The foraging territory of subterranean termites varies with species. Workers from one species may forage in a 10 m2 foraging territory, whereas workers from another species may forage in a 100 m2 area or within a 100 m linear distance.
  • It seems that there might be geographic differences in the size and number of colonies, influenced by food availability and environmental factors.