Termites

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Termites

Termites are slender, social insects, ranging in size from 0.007-0.072 in (2-22 mm) long. The reproductive members of the species have wing spans of 0.03-0.3 in (10-90 mm). Inhabiting nests of their own construction, they live in permanent and often highly developed communities. While termites thrive in warm, humid environments, some species have also adapted to open savannas and temperate zones. They are most commonly found in the tropical parts of Africa, Southeast Asia, Australia, and the Americas.

Termites belong to the order Isoptera, which includes seven families of termites, containing about 200 genera and about 2,300 species. The families are: (1) the Mastotermitidae, (2) the Kalotermitidae, (3) the Termopsidae, (4) the Hodotermitidae, (5) the Rhinotermitidae, (6) the Serritermitidae, and (7) the Termitidae. The first five families are referred to as the lower termites, while the last two are known as the higher termites.

The classification into lower and higher termites refers to the termites’ level of evolution, both in terms of behavior and anatomy. The higher termites have a more complex and developed social structure and build a more complex and varied nest. The most advanced nests start below the ground and form a mound above. A termite nest in Australia measured almost 20 ft (6.66 m) high and 98 ft (33 m) around. Three-quarters of all species of termites belong to the higher termite groups.

Caste system

The individuals making up a termite community are anatomically and functionally distinct from each other, depending upon their role within the community. The particular duty that each termite performs determines the specific caste to which each termite belongs. Each caste can perform only a certain task, and individual termites cannot stay alive without the rest of the colony. In total, there are four basic kinds of adult termite castes: the king and queen (primary reproductives), the supplementary reproductives, the soldiers, and the workers.

Reproductives

there are two reproductive castes providing for the continuation of the species. The primary reproductive caste—known as alates—consists of potential kings and queens. At a specific time each year, depending on the species and environment, a swarm of these alates leaves the original nest to start a new colony. The vast majority of swarming alates fall prey to birds, bats, lizards, snakes, and ants. When the male and female alates land, they shed their wings and look for mates. Once the pairing occurs, they run on the ground in tandem, the female ahead of the male, looking for the site on which to build their new nest.

The supplementary reproductives develop functional reproductive organs but never leave the parent colony. Their purpose is to act as substitutes for the king or queen if either or both dies. Further, female reproductives can supplement the queen’s egg-laying volume, should her egg-laying capacity prove insufficient to maintain the colony.

The nesting location chosen by the alates is highly dependent upon the particular species of termite. Some species prefer to nest in the ground, while others prefer to nest in wood. Regardless of the nest, the pair digs a chamber, closes it off from the outside world, and never leaves it again. The pair mates in the chamber, and the female lays the eggs. Her first laying contains relatively few eggs. The young king and queen care for their larvae for four to six months. During this period, wood termites get the sustenance they need from the wood in their nests, while soil termites feed their young with the excess fat stored in their own bodies and by digesting their now-useless wing muscles.

Newly hatched termite larvae are tiny, measuring about 0.08 in (2 mm) in length. Their coats are colorless and their bodies are soft. Furthermore, they are blind; their main sensory organs are their antennae, but they also have a series of small receptors situated on their heads.

After hatching, the young termites—or nymphs— have the general appearance of adult termites. They continue to grow and molt at intervals. After several stages of development, some finally become sexually mature individuals with wings. Others either become workers or soldiers. Both the workers and the soldiers—which are usually blind, and always infertile and wingless—are the result of specialized, incomplete development.

Workers

the workers form by far the largest caste and live exclusively underground; they are pale, have large toughened heads, and lack eyes. When the first workers are old enough to leave the nest, they begin to undertake their multiple duties. First, they search for food, leaving the queen free to devote all of her time to egg-laying. Eventually, the workers provide food for the king, queen, larvae, and soldiers. Dead wood is the main part of a worker termite’s diet. Often, workers eat wood before returning to the colony with it. In such cases, they partially digest it and transform it into a milky liquid. When they reach the colony, the workers feed the other termites through regurgitation; this form of food is called stomodeal food.

Most species of termite eat wood, but their digestive enzymes are not able to break down the nutritious part of the wood, called cellulose. To do this, termites have the help of microorganisms residing in their bodies that break down the cellulose into a substance that they can digest.

The workers also take part in building the colony. In the majority of species, the workers dig underground systems of tunnels. They create complex structures, which protect the inhabitants from their enemies. Because some nests contain as many as three million termites, the nests need the right level of oxygen and carbon dioxide for the members to survive. Therefore, workers build nests with ventilation systems regulating the colony’s environment. It is thought that intestinal gases, including methane, rise to the top of the nest and diffuse through the walls and out of venting shafts.

Another task that the workers must carry out is caring for the colony’s young. When the queen lays her second series of eggs—about one month after her initial laying—the workers take the larvae into the brooding chamber where they care for them. As part of their care, the workers turn over the eggs periodically and check them for signs of parasite damage.

Soldiers

the soldier termites’ main responsibility is defending the colony. Unlike other termites, soldiers have large armor-plated heads, a tough outer skeleton, and sometimes have glands for squirting poison at their enemies. Furthermore, the soldiers are equipped with biting mandibles, which include cutting edge teeth and even hooks.

Although termites are often preyed upon by aardvarks, reptiles, and other amphibians, their main predators are army and chirping ants. Even though the soldiers are blind, they can sense intruders with their antennae. To warn the colony, the soldiers beat their heads against the ground. Soldiers are never able to feed themselves.

The mature colony

Deep within the nest, protected by soldiers and cared for by workers, the queen begins to grow. While her head and thorax do not change, her abdomen increases in size as her ovaries enlarge and her egg-laying capacity increases. In some highly evolved species with extraordinarily large colonies, the queen can swell to more than 5.5 in (77 cm) in length and 1.5 in (3.81 cm) in diameter; thus, her abdomen swells to about 200 to 300 times it original size. In such a state, the queen is incapacitated and cannot feed herself.

By her third year, the queen reaches the peak of her egg production, when she typically lays over 30,000 eggs per day. The most fertile queens belong to the species Odontotermes obesus, which can lay about one egg per second or about 86,400 eggs each day. In all species, the king, her constant companion, changes very little throughout his life.