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Isoptera is the insect order to which the termites belong. The name Isoptera (iso-ptera = "equal-winged") refers to the adult primary reproductives which possess two pairs of equal length wings. The body plan or morphology of termites is rather simple indicating that they diverged very early in insect evolution from a generalized insect ancestor with gradual metamorphosis and the ability to fold the wings flat over the back. Although simple in morphology they are advanced in social behaviour.
Termites are most closely related to cockroaches (Blattaria). The primitive termite genus, Mastotermes, like cockroaches, lays its eggs in an ootheca-like mass and has a folded anal lobe in the hind wing.
Recent tabulations indicate that as of 1995 there were approximately 2,753 validly named termite species in 285 genera in the world.
The vast majority of termite species occur in the tropics. Only one species is resident in Ontario, the eastern subterranean termite, Reticulitermes flavipes (Kollar).
Like ants, wasps and bees, termites are social insects. They exhibit brood care within their social community or "colony". A colony is really just a very large family of insects. Within this family there is an overlap of parent and offspring generations. Some of the offspring diverge from the normal course of development to become various castes. Unlike most insects, which have only one linear developmental pathway, termites have branching developmental pathways. Therefore, we say that they are polymorphic.
The Termite Family.
Termites are said to live in "colonies" but this is misleading. A colony is really just a family of insects. One of the most profound and defining attributes of the termite family is that it is built on monogamy. Termites are faithful. They are probably the most monogamous group of animals on earth. The evolutionary outcome of this commitment to monogamy is a large and integrated family. As far as biologists know, termite colonies are the most sophisticated families ever to evolve in the universe. Human families are not nearly as advanced. Humans, in contrast to termites, have the most advanced, non-family based type of social system known in the universe.
Termite colonies are comprised of three basic castes: workers, soldiers, and reproductives.
Eggs hatch into tiny immatures incapable of feeding called larvae. Larvae are totipotent which means that they are genetically capable of developing into any caste. Time of year, diet, and pheromones all play a role in determining which developmental pathway any given termite follows.
Workers comprise the bulk of the population. In lower termites there is a false worker caste called pseudergates who retain the potential to become alates. Workers feed all the dependent castes: larvae, nymphs, soldiers and reproductives. They also dig tunnels, locate food and water, maintain colony atmospheric homeostasis, and build and repair the nest. In some species their job description also includes mushroom gardening.
Soldiers develop from nymphs, pseudergates, or workers. The metamorphosis to a soldier takes two moults. The transition stage is called a presoldier. With their specialized defensive weaponry, soldiers provide colony defence against numerous predators such as ants.
Reproductives develop either from alates or neotenics. Alates are winged termites. Each species produces a cohort of alates at a particular season. The alates of each species fly at a unique time of day and under specific conditions. In Toronto, the alates of Reticulitermes flavipes appear from February through May and usually fly about midday on warm days. The alates develop from nymphs by growing wings and compound eyes. After flying, the alates break off their wings along a basal suture and are then called dealates. Dealates form tandem courtship pairs, and after a brief courtship run, dig into the soil adjacent to wood, mate, and start a family. The offspring constitute the colony. The founding reproductive pair is now the queen and king of the new colony.
Primary reproductive females, or queens, vary in size depending on the species. Tropical queens may measure 10 centimetres in length and produce thousands of eggs a day.
The enlarged abdomen makes her relatively immobile and dependent on the workers. She is licked and fed constantly and closely attended by her relatively puny mate, the king. There is usually just one pair of primary reproductives per colony but some species have a low incidence of polygamy.
Secondary reproductives may develop from either unflown alates (=adultoids), nymphs (=nymphoids) or workers (=ergatoids).
If a primary reproductives dies it is usually quickly replaced by a secondary reproductive of the same sex. In the more primitive wood inhabiting termites large numbers of pseudo workers quickly moult to neotenics when removed from the pheromonal inhibition of a primary reproductive.
These newly moulted neotenics then engage in lethal fights with same sex siblings, eventually resulting in the survival of only one secondary replacement reproductive of each sex. It is ironic that these termites which are so co-operative as immatures are so viscously competitive upon maturation. Unlike primary reproductives that almost always outbreed, secondary reproductives always mate incestuously resulting in inbreeding.
Nymphoids are the main source of reproduction in our resident Reticulitermes flavipes.
Termite Ecology.
Termites feed on dead, plant cell wall material, such as wood, leaf litter, roots, dead herbs and grass, dung, and humus. Chemically, their food can be characterized as lignocellulosic matter, which is the most abundant organic material in the biosphere. Termites are able to digest cellulose, and some species can also digest lignin, with the assistance of symbiotic intestinal protozoa and bacteria.
Many termites also have symbiotic relations with nitrogen fixing bacteria. In converting lignocellulosic biomass to insect biomass, termite production supports a large proportion of tropical vertebrate biodiversity, including many species of amphibians, reptiles, birds, and ground foraging insectivorous mammals.
Thanks to
Timothy G. Myles, Ph.D.
Director, Urban Entomology Program
Faculty of Forestry, University of Toronto
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