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132 IVII. Zoocoenological characteristics
64 Formica rufa were found, and 147 larvae also contained larvae (a total of
1598) of Eulophus abdominalis.
The abundance values obtained as a result look totally different to those
that were realised using the same spatial reference that we used for one
population (for a corrumpent, let us say). From these numbers, that shed
light on the relative abundance relations of a zoocoenosis (or a catena), we
can draw important conclusions. If, for example, at a subseguent census, we
find that the number of larvae on 100 leaves decreased from 600 to 546, while
the number of ants increased from 4.6 to 29.8, solely based on these numbers,
we can assume that the ants forage in the canopy not just for the looper
caterpillars because, if that were the case, their numbers should have decreased.
There can be two possibilities: that the ants are related to other populations
as well, or their presence in the canopy is aimless meandering (see Elton
1927, 56: “All cold-blooded animals and a large number of warm-blooded
ones spend an unexpectedly large proportion of their time doing nothing at
all, or at any rate, nothing in particular”). In the former case, ant numbers
should also be related to these populations (that is, the combined populations
of Operophthera + Archips + Pandemis spp.), meaning that F rufa cannot be
constrained in one catena, but associates at the level of a catenarium and, in
considering this, we should not overestimate the obstant role of ants in the
regulations of the Operophthera population (see p. 111 - degree of obstancy).
Thus, the numbers representing abundance are full of detail, providing
additional information about the borders of the zoocoenosis its internal
trophic relationships, and are not merely “dead” columns of numbers, that
we are unable to explore and analyse.
The value of abundance should express the number of individuals in the
zoocoenosis. However, we have to register the number of individuals in a
unit of space and, perhaps, even combined with a unit of time; the result
obtained can only tell us that, in the examined part of space, the size of certain
populations had certain values. Anything further relies on assumptions, and
the more studies we do, the closer we get to the truth, without being able to
reach it with our current methods.
Abundance can have two meanings, depending on whether it refers to the
number of individuals in a population or the number of populations (see
Tischlers (1950) “Individuenabundanz vs. Artenabundanz”). Both are
informative because the population density can refer to the role ofthe given
population group in the zoocoenosis, whilst the species density can refer to
the completeness of the zoocoenosis. The high abundance of some population
can be a cause of low species abundance in others, because those other
populations are squeezed out. We can see this in the case of Diaspidiotus
perniciosus, whose high abundance can cause the absence of Sphaerolecanium
prunastri, D. ostreaeformis, and Epidiaspis leperii.