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TERMITE,
common name for numerous species of social insects, comprising
the order Isoptera, that can damage wooden structures such as furniture
or houses. Of about 2000 known species, most are distributed in
tropical countries, and some inhabit the temperate regions of North
and South America; two have become established in southern Europe.
Termites are known also as white ants, a misnomer based on superficial
similarities in the appearance and habits of these two insect groups.
True ants belong to a more advanced insect order, the Hymenoptera,
which includes also the bees and the wasps. Termites are relatively primitive;
they have thick waists and soft bodies and undergo incomplete metamorphosis.
Nevertheless, they have developed remarkable patterns of social
behavior that are almost as elaborate as those of the ants, social bees,
and wasps.
No solitary termites exist. A colony may number from 100 to
more than 1 million termites. Excluding the immature forms, called
nymphs, a colony consists of several structurally differentiated
forms living together as castes with different functions in community
life. In socially advanced species, three principal castes exist:
the reproductives, the soldiers, and the workers. Both the reproductives and
the soldiers occur in two or three distinguishable forms, each specialized
for a role in the division of labor in the colony. All forms comprise
individuals of both sexes, but only in the reproductives do the
sexual organs undergo complete development.
Among the reproductives are dark-colored males and females
with fully developed wings and compound eyes. At maturity, they
leave the parental nest in swarms. After the flight, they shed their
wings and mate. A new colony is then established by a male and female
who become primary reproductives, that is, the king and queen, whose
sole occupation is the production of eggs. Termite kings and queens
are longer-lived than other termites, and the queens are larger
than other members of their colony. In certain tropical species,
the king and queen live for ten years, and the queen grows to an
enormous size, sometimes as much as 20,000 times the size of the
worker. The abdomen becomes so distended with eggs that the queen
is unable to move about. The eggs are laid at a prodigious rate
that totals about 30,000 a day in some species. Most termite colonies have
only one royal pair.
Apart from the reproductives, all castes are sterile and wingless
and have whitish bodies. Typically, the worker caste is the most
numerous, and workers are the smallest of the adult forms. Workers
build and provision the nest, tend the eggs, and feed and groom
all the other members of the community. In some species, no true
worker caste exists; undifferentiated nymphs do the work in these
colonies. To defend the colony, all species have soldiers with greatly
enlarged heads. In some species, the soldiers are equipped with huge
jaws; in others, they have long snouts that can eject a sticky,
poisonous substance to render an enemy helpless.
Caste differentiation was long believed to be hereditary,
but investigations have since demonstrated that nymphs may develop
into specialized forms as the need arises within the colony. Hormonelike
substances secreted at the body surfaces of the royal pair serve
to inhibit the production of primary reproductives. These substances,
which are licked off by the workers during grooming, are transmitted,
probably with food, to the other members. In the absence of these
inhibitory exudates after the royal pair dies, nymphs at a particular stage
in their molting cycle rapidly develop reproductive organs and become
fertile. A similar process operates in maintaining the required
number of soldiers in the community.
Termites feed mainly on wood or other materials containing
cellulose. The cellulose is partially digested by protozoans living
symbiotically in the intestines of the worker. Enzymes produced
by the protozoans break down the cellulose into components that
can be assimilated by the termites. Digested cellulose is distributed
by the workers to members lacking the protozoans. Some species feed
on vegetable molds that they cultivate. Others obtain a fluid secreted
by beetles known as termitophiles, that live as guests within the
termite community.
Termite nests, called termitaries, vary widely. The nests
of certain tropical species are huge moundlike structures, often
6 m (20 ft) in height. These mounds have extremely hard walls, constructed
from bits of soil cemented with saliva and baked by the sun. Inside
the walls are numerous chambers and galleries, interconnected by
a complex network of passageways. Ventilation and drainage are provided,
and heat required for hatching the eggs is obtained from the fermentation
of organic matter, which is stored in the chambers serving as nurseries.
Of more than 55 species common in the U.S., the majority build
their nests underground. The subterranean termites are extremely
destructive, because they tunnel their way to wooden structures,
into which they burrow to obtain food. Given enough time, they will
feed on the wood until nothing is left but a shell.
To prevent damage by termites, building foundations should
be built of materials other than wood. Because cracks may develop
in such foundations and provide passageways to the wooden parts
of the structure, the soil should be treated first with an insecticide
to discourage termitic incursions. Control is obtained also by using
wood treated with creosote or some other poisonous chemical. Because
most worker termites cannot live without moisture, the termitaries
should be exposed to dry air.