SOIL ORGANISMS - Soil Ecology - page 310

their food resources; it includes many subterranean and epigeal nesting species and those
that construct arboreal nests on the outsides of tree branches. Species included in this
group represent a wide variety of feeding habits, including wood-feeding, grass harvest-
ing and litter-feeding, soil-wood and soil-feeding species.
The initial primitive condition is considered to be the one-piece type since it resem-
bles that of the presumedly ancestral wood-feeding cockroaches. Evolution of life types
is considered to have proceeded to the intermediate and then the separate types.
The different ecological groupings and their environmental impacts are considered
further in Chapter IV.5.2.1.

4.3.2.3 Population densities and biomasses

Termite colonies are difficult to sample accurately and most population estimates for
termite colonies must be regarded as minima. Difficulties arise in enumerating whole
colonies since a proportion of the individuals may be absent foraging or escape from the
nest during sampling. Subterranean termites may have large diffuse colonies with patchy
distributions and complete sampling would often require the separation of enormous
amounts of soil. Finally, the small size of termites is a serious obstacle to their enumeration.
Darlington (1984), for example, found that fumigation of termitaria prior to sampling
increased colony population estimates substantially. Where fumigation was omitted,
differences in the estimation of caste proportions also resulted; in mature mounds most
of the eggs had disappeared and estimates of larvae were diminished by an order of
magnitude. Separation of termites from mound materials using wet sieving methods
gives biomass estimates up to 5-10 times higher than direct hand sorting (see, e.g.,
Lavelle and Kohlmann, 1984).
Isotopic methods have been used to estimate populations, although with varied success.
It appears that isotope dilution methods overestimate colony populations because of
rapid elimination of the isotopic 'label' into the nest environment. However, the use of
isotopes as labels in mark:recapture techniques is apparently more successful (Easey
and Holt, 1989).

Colony population estimates
Despite the methodological problems considered above, colony sizes have now been
estimated for a range of termite species revealing populations ranging from a few tens
of individuals to several millions. Small colonies may simply be juvenile or they may be
constrained by the size of their resources. However, the mature colony size is generally
related to the size and quality of the food base. Large food supplies lead to bigger
colonies, longer life cycle spans, later colony maturity and greater numbers of supple-
mentary and replacement reproductives that may be present in addition to, or replace the
original reproductive pair (Lenz, 1994).
The colonies of 'dry wood' termites are generally small, less than ca. 3000 individuals.
Many Kalotermitidae have small nests, often formed in the dead branch stubs of trees and
in similar locations. Kalotermes flavicollis is a Mediterranean dry wood feeding species that
forms small colonies in the dead and diseased wood of living trees (Harris, 1970). Reported
colony sizes for K. flavicollis range up to a maximum of 3250 workers (Noirot, 1990).