Termite fossils date from about 130 million years ago, but they probably evolved much earlier from a primitive, wood-eating, roachlike ancestor. There are about 1,900 termite species divided among six families. Five of the families are considered primitive or lower termites because, like their primitive wood-eating roach relatives, they harbor symbiotic protozoa in the hindgut that digest cellulose. Without these protozoans, the termites would starve to death. The higher termite family, Termitidae, is the largest family, containing about 75 percent of all termite species. Higher termites may be able to digest cellulose themselves, or bacteria in the gut may secrete enzymes to aid in digestion.
Caste System and Nests
Termites are notable for their highly organized societies. Because most termites are effectively deaf and blind, they communicate through touch, smell, and taste. Most species are divided into castes of reproductives, workers, and soldiers. Normally, there is only one reproducing pair, the primary reproductives, or queen and king. Secondary reproductives are present, too, in case the queen or king dies. The sterile workers and soldiers are of both sexes.Workers care for the eggs and nymphs, provide food for the nymphs, soldiers, and reproductives, and construct, repair, and maintain the nest. Soldiers have evolved modified heads and jaws for defending the nest. The heads are large and hard with powerful, scissorlike mandibles or long, tubular snouts that squirt sticky chemicals. Some soldiers have both formidable jaws and chemical weapons. Termites are vulnerable to desiccation, changes in temperature, and hungry ants, birds, aardvarks, and other predators. They maintain a moist, temperature-controlled, safe environment by constructing nests. Dry-wood termites never touch the soil but nest in the wood they feed upon, gnawing out tunnels and chambers inside living tree trunks and branches, rotting logs, or furniture and wooden buildings. Subterranean termites must maintain contact with the soil for food sources such as grass and humus or for moisture. Many species are master builders, constructing elaborate nests of carton in trees with covered runways leading to the ground or mounds in the soil complete with ventilation shafts, towering chimneys up to 9 meters (29.5 feet) high, and even fungus gardens to supplement their cellulose diet. Although the architecture varies widely, most nests provide an inner chamber for the egg-laying queen and her king, and areas for brood chambers and food storage.
Unlike insects such as butterflies, termites undergo incomplete or gradual metamorphosis. From the time they hatch, immature termites looks like pale, wingless, miniature versions of adults. To allow for growth, these nymphs molt periodically, shedding and then eating their outer skin. All nymphs start out the same. The correct balance among the castes appears to be maintained by bodily secretions containing hormones that are transferred by licking, but the mechanism is not yet understood. New colonies are usually formed when alates swarm during certain seasons. Workers prepare by digging tunnels to the surface, with exit holes and sometimes launching platforms. Once the alates leave, soldiers prevent them from returning. They are weak fliers and usually descend within a few hundred meters of the original nest. Wings are shed after landing. Females attract males by raising the abdomen and emitting a pheromone. Before mating, pairs locate a likely site for a nest and seal the entrance with fecal matter. The first batch of eggs is usually small. The king and queen take care of the eggs until there are enough older nymphs to take over. After a few years, the queen's ovaries and abdomen increase in size, and her egg laying accelerates. She may grow to 11 centimeters (4.3 inches) long and produce up to 36,000 eggs per day.
Order: Isoptera (termites)
Geographical location: Every continent except Antarctica
Habitat: Majority of species inhabit tropical rain forests but many live in temperate and subtropical zones, deserts, or mountains up to an altitude of 2,500 meters (8,200 feet) Gestational period: Varies but averages approximately two weeks
Life span: The primary queen and king may live to seventy years, although ten or twenty years is more common; workers and soldiers live from two to five years
Special anatomy: Isoptera means "equal wings"-adult reproductives have two oval-shaped pairs of overlapping wings of nearly equal length; small to medium-sized, very soft, usually light-colored bodies; thorax fused with the abdomen; workers have specialized mouthparts for chewing wood, while soldiers' mouthparts have been modified for fighting; except for reproductives, termites usually lack eyes
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