Subterranean Termites
 

Richard M. Houseman
Department of Entomology

There are approximately 2,500 species of termites worldwide. Most are found in tropical areas, while relatively few live in colder climates. Only about 45 species are found in the United States, and most of these are located in southern states. Four species of termites are reported to occur naturally in Missouri. All of these species are closely related and belong to the genus Reticulitermes.
Termites are generally grouped into categories based on the habitat in which they live. Drywood and dampwood termites live inside wood of varying levels of decay and moisture content. Subterranean termites live in the soil and wood that is in contact with soil. All of Missouri's native Reticulitermes termites are subterranean. Subterranean termites are found throughout most of the continental United States, while wood-dwelling species occur in the coastal and southernmost tier of states. Wood-dwelling termites can be introduced into other locations of the country through the transport of wood products, although they normally do not spread or become established in these locations.

In natural ecosystems termites are considered beneficial because they help release nutrients from dead wood and other cellulose materials into the soil. In human environments, they are considered serious pests. Due to their widespread distribution, subterranean termites are responsible for most of the termite damage caused annually in the United States. Approximately $4.5 billion is spent annually in the United States to control subterranean termite infestations and repair damage they cause.
 

Biology

Termites are social insects like ants, bees and wasps. Social insects live in large groups, share a nest and share important biological roles among individuals within a colony. In termite colonies, important biological roles are divided among physically distinct termites called castes. Termite castes include eggs, larvae, workers, soldiers, nymphs and reproductives (Figure 2). The percentage of the colony in each caste is regulated by chemical signals, which vary between different species and groups of termites.

 

Figure 2
Life history of subterranean termites (Reticulitermes spp.). After hatching, termites may pass through many, but not all, of the stages shown here. These stages are

1. Eggs
2. Larva
3. Larva
4. Worker
5. Worker
6. Soldier
7. Nymph
8. Swarmer
    

Reproductives
This is the adult caste that produces offspring. There is always at least one male and one female in an active colony. Primary reproductives are shiny brownish to black in color. They are produced in mature colonies and emerge at certain seasons of the year to make dispersal flights. During the period they are called swarmers (Figure 2). Swarmers are seldom produced until the colony is more than three years old.
In the case of the eastern subterranean termite, swarming flights occur in Missouri during the spring months, usually on a warm, sunny day following rain. Sometimes, termite swarmers are confused with ant swarmers during this time, but the two are easily distinguished from one another (Figure 3). After flying away from their home colony, termite swarmers shed their wings and pair up. Each pair starts a new colony by constructing a protective cell in the soil adjacent to wood or other food source. Mating and egg production begin in this cell. These activities constitute the beginning of a new subterranean termite colony.

Figure 3
Differences in body form between winged termites and winged ants. Winged termites are distinguished by

• Four cloudy-white, equal-sized wings
• Straight antennae
• A waist equally as broad as the rest of the body

Winged ants are distinguished by

• Four clear, unequal-sized wings
• Bent antennae
• A waist that is narrower than the body
   

Eggs
Subterranean termite queens lay clusters of eggs (Figure 2), which look like small, translucent jelly beans. The reproductives care for the first batch of eggs, but thereafter, worker termites care for the eggs, keeping them clean from bacteria, fungi and other microorganisms in the soil.
Larvae
These are small termites that have just hatched from the egg and have not molted more than once (Figure 2). They are characterized by their small size, soft head capsules and mouthparts, and their absence of coloration. They are dependent on worker termites to feed them.
Workers
Also called pseudergates, these termites are creamy white and soft bodied, with a darker head and hardened mouthparts (Figure 2). Workers are the most common caste in a termite colony and are responsible for many of the activities in the colony. Workers locate and consume wood, feed and groom the other castes, and build and repair tunnel systems. Because subterranean termites are susceptible to drying out when exposed to open air, the nest-building activities of the worker caste are critical for colony survival. In addition to tunneling, subterranean termite workers build shelter tubes to serve as protected passageways from the soil to aboveground food sources.
Even after reaching maturity, workers continue to molt periodically throughout their lives with no increase in size. After every molt, workers get a new set of mouthparts. If isolated, individual workers may molt into a stage that is capable of reproduction. Workers that go through this change are called tertiary reproductives.
Soldiers
Relatively few soldiers are found within a colony. They are responsible for colony defense. Their enlarged heads and long mandibles are adapted to plug holes in the tunnels and inflict a painful bite on invading enemies (Figure 2). Soldiers rely on the worker caste to feed them.
Nymphs
Termites in this caste are preparing to molt into fully winged termites and leave the nest to start new colonies (Figure 2). If isolated during this stage, individual nymphs can become capable of reproduction. Nymphs that go through this change are called secondary reproductives.

Reference : University Of Missouri