Agriculture Reference
In-Depth Information
v.
Arboreal nests
Arboreal nests are built on the outsides of trees, frequently in the angles between branches.
They are built only by the Termitidae and by species in all subfamilies except the
Macrotermitinae. They are most frequent in the Nasutitermitinae, common in the widespread
genus
Microcerotermes,
but also occur in
Speculitermes
(Indomalayan) and
Anoplotermes
(Neotropical) (Noirot, 1970). The latter has small fragile nests that may
hang from foliage although little is known of their function (Araujo, 1970). Australian
examples of arboreal-nesting termites include
Nasutitermes graveolus
and
Nasutitermes
walkeri,
two species that build nests constructed of carton on the exterior of trees, often
many metres above the ground (Chapter III.4.3.2.2).
vi.
In the nests of other termites
Inquiline termites occur in both occupied and abandoned mounds built by many
termites although no communication normally takes place between the portions
occupied by different species. Noirot (1970) reported that as many as 10 species
may occur in a few cubic decimetres of the mounds of the soil feeder
Cubitermes
sp..
Many soil-feeding species occur as inquilines within the mounds of other termites
(see, for example, Miller, 1991).
Another common situation is the acquisition of space within an existing mound by
a termite different from the original builder which then constructs its own mound on top
of the original. In northern Australia, a common compound mound type is that formed
by the construction of a conical mound of the litter-feeder
Amitermes vitiosus
on the
surface of a low mound of the grass harvester
Drepanotermes rubriceps.
Abundance and composition
Epigeal mounds may be abundant: Aloni and Soyer (1987) report populations of more
than 5000 mounds per hectare from Zaïre, principally belonging to the soil-feeding
Cubitermes
species. The above-ground sections of termite mounds may weigh many
tonnes per hectare and occupy considerable proportions of the soil surface, depending
on their type. In tropical Australia, mound populations may number up to 1100
representing approximately 62 Mg of soil and covering 1.7 % of the sampled area
(Wood and Lee, 1971). Median mound mass for the 58 Australian sites recorded by
Spain
et al.
(1983b) was, however, only 20 Mg (inter-quartile range 15-25) and
the median area covered by their bases just 0.8 % of the sampled sites (inter-quartile
range 0.5-1.1). Similar estimates from African sites range up to 10 % of the area sampled
although Meyer (1960) estimated that the bases of mounds at one site covered an excep-
tional 33 % of the soil surface, representing an estimated dry mass of 2400 Mg
The spatial distributions of termite mounds may be random, aggregated or over-
dispersed. Where mound populations are high, they frequently tend to over-dispersion
(Spain
et al
., 1986) suggesting that such termite populations can utilise a substantial
proportion of the organic resources available to them in the landscape. This is reinforced
by the denudation and dietary shifts that occur during drought years (Lepage, 1981a;
Watson and Gay, 1970) or as a consequence of altered or intensified land use (Wood
and Pearce, 1991).
