SOIL ORGANISMS - Soil Ecology - page 302

Colonies progress from juvenile to mature stages and eventually decline (Bodot, 1969).
The juvenile stage is differentiated from the adult by the production of reproductives.
Caste proportions alter in characteristic ways during the different stages of colony
development In Kenya, juvenile colonies of the litter-feeding and fungus-cultivating ter-
mite Macrotermes michaelseni grow rapidly and the population comprises 50 % or more
of larvae. On reaching a population of ca. 1.2 million, the colonies become mature and
start to release reproductives. The proportion of larvae then falls to ca. 41 % and the colony
growth rate subsequently declines (Darlington and Dransfield, 1987). In the final or senile
stage, the queen's fecundity declines and the colony vegetates and dies. In some species,
supplementary reproductives may assume the former queen's role and these termite
colonies are potentially longeval. Although the reason is unknown, all colonies
eventually decline and die, even in the apparent absence of obvious causative factors,
Colonies may exist for considerable periods; those of the Australian species
Drepanotermes perniger may survive for substantially more than 50 years (Watson
et al ., 1988).
Movements and dissemination
As stated above, the principal dispersal mechanism among the termites is the seasonal
release of primary reproductives from established colonies that occurs during the wetter
periods of the year. However, shorter distance dispersal may occur through sociotomy
(Grassé,1984).
Neither individual termites nor colonies normally travel long distances since they are
constrained to live within their territory borders or, as in certain lower termites, within
their food materials. Most termites only move in sheltered locations within galleries
distributed vertically and horizontally in the soil or within their food materials. While a
range of grass-harvesting and litter-feeding termites regularly forage unprotected on
the surface, most species move and feed beneath thin covers or workings built of soil
particles and plant materials which protect them from desiccation and from predators.
The scales of termite movement may be very small, as in the dry wood termites that
feed and nest in small pieces of wood on a single tree. Litter-feeding and certain wood
feeding termites may move up to radii of ca . 50 metres from the central nest, as recorded
for Macrotermes michaelseni in Kenya (Darlington, 1982). The scale of movement of
the processional termite ( Hospitalitermes hospitalis ) during foraging for lichens in
Brunei may be more than 65 m (Jones and Gathorne-Hardy, 1995).
Feeding habits and digestive processes
A diversity of organic food materials is utilised by termites although most feed predom-
inantly on lignocellulose-rich or partly-humified dead plant materials. Actual diet depends
on the ecological strategies adopted by individual species and this is determined by the
part of the decay continuum from which they select their food materials (Chapter
IV.5.2.1). Certain termite species regularly attack a wide range of materials, including
plastics, the softer metals and other non-assimilable materials (Gay and Calaby, 1970). The
nutritional ecology of termites has been reviewed by Waller and La Fage (1987) and,
more recently, by Lenz (1994) for wood-feeding species.