FUNCTIONING OF THE SOIL SYSTEM - Soil Ecology - page 503

others such as the harvester Hodotermes mossambicus betray their presence by surface
soil dumps and other structures (Coaton, 1958). Nests may be diffuse with little
differentiation between the galleries with transitional forms culminating in a clearly-
recognisable nest area and differentiated structures (Noirot, 1970). Heterotermes spp.
provide examples of species with diffuse, little-differentiated nest systems which
occur in the soil, in or under logs and stumps and in the mounds of other termites
(Watson and Gay, 1991).
In contrast, some groups, such as the fungus-cultivators (Macrotermitinae), build
highly complex subterranean nests that may comprise multiple nesting chambers,
food stores and fungus chambers with interlinking galleries (Darlington, 1994).
iii. Epigeal nests
Epigeal termite mounds of diverse types are a common feature of many tropical
landscapes. The mounds are normally built by higher termites belonging to a range of
ecological strategies, including grass harvesters, litter feeders, wood-feeding species
and, in some locations, soil-wood and soil feeders. A number of fungus-cultivating
termites also build epigeal mounds. The epigeal and semi-epigeal mounds of some
soil-wood and soil feeders are occasionally numerous and the species of this group are
therefore of ecological and pedological importance, although their biological role is
currently ill-defined. Certain Australian Coptotermes species (family Rhinotermitidae)
are among the few lower termites to build epigeal mounds, although they may not do
so at all locations within their ranges.
The distinction between subterranean and epigeal nesting locations may be some-
what arbitrary. Epigeal mounds normally originate from subterranean beginnings or
from a colony established in wood and most of these mounds have at least some part
of their structure below the ground surface. A number of intermediate forms occur
between epigeal and the wholly subterranean forms. Miller (1991) reports that the nest
structure of the Australian soil-wood feeder Paracapritermes secundus (family
Termitidae) is largely underground but that the tip protrudes above the litter within its
rainforest habitat,
Epigeal mounds occur in a range of sizes from a few centimetres to almost 9 m tall
in the Australian grass harvester, Nasutitermes triodiae (Lee and Wood, 1971a). Noirot
(1970) distinguishes two major types: those comprising a series of essentially similar
chambers and those with more differentiated internal structures. The mounds of the
tropical Australian litter-feeder Amitermes laurensis and Noditermes aburiensis
(both Termitidae) from the Côte d'Ivoire are of the first type while the fungus-cultivating
termites of the sub-family Macrotermitinae may build complex nests that include their
fungus chambers (Noirot, 1970).
iv. Intermediate nests
These nests are usually associated with the bases of trees and have clear connections to
the ground. The builders of such structures are often soil or soil-wood feeders in contrast
to the predominantly wood-feeding termites that construct arboreal nests (Martius, 1994).