12
A. MACFADYEN
lated method could successfully contribute to the study of feeding behaviour of small arthropods.
B. BEHAVIOUR-TYPE METHODS
The methods discussed in this and the next section differ from the
above in that they are designed to remove the fauna from the soil. This
can be done in two fundamentally different ways, firstly, one can take
advantage of differences in physical properties such as density and wettability between animal material on the one hand and plant and mineral
matter on the other to remove the fauna mechanically. Secondly, one
can make use of the animals’ own powers of locomotion and response
to physical stimuli to attract or repel them away from the soil. Both
these principles have inherent weaknesses and neither has yet produced a universal extraction method. Thus the first which are here
called “mechanical” methods are more especially restricted to certain
groups on account of the great range of density and surface features
found in animals and are particularly inefficient at separating animals
from large quantities of plant matter. On the other hand they work best
in arable soils containing high-proportions of minerals, especially clay,
under which conditions the second type are least efficient. Behaviourtype methods, as we shall call them also tend to be fairly selective and
are useless for removing immobile stages such as eggs and pupae, unless
these are deliberately hatched to a mobile condition. They are, on the
other hand the only available methods for most media containing much
plant matter such as litter and grassland mats.
Considering first the behaviour-type methods it would seem sensi ble
to classify these in terms of the kinds of stimuli such as heat, humidity,
and chemical attractants and repellents used to induce the animals to
leave the soil. However, in practice most practical methods employ a
number of stimuli together and it is more convenient to consider firstly
those methods which operate in the field on untouched soil and secondly
those which are applied in the laboratory to soil or litter sample-units or
cores which have been removed from the habitat.
1. Field Apparatus: Pitf.11 and Baited Traps
Pitfall traps do not necessarily involve the application of specific
stimuli ; frequently they depend simply on chance wanderings of surface
forms. They can be made very simply from glass jam jars or (less suitably) tins and can be left empty or contain a layer of preservative such
as formalin. Many refinements have been described especially from the
Kiel school lead by Tischler (see Heydemann, 1958). In damp climates
it is desirable to arrange a rain-shedding cover and very dilute phenyl
mercuric acetate solution has the advantage over formalin of being non-
A. MACFADYEN
lated method could successfully contribute to the study of feeding behaviour of small arthropods.
B. BEHAVIOUR-TYPE METHODS
The methods discussed in this and the next section differ from the
above in that they are designed to remove the fauna from the soil. This
can be done in two fundamentally different ways, firstly, one can take
advantage of differences in physical properties such as density and wettability between animal material on the one hand and plant and mineral
matter on the other to remove the fauna mechanically. Secondly, one
can make use of the animals’ own powers of locomotion and response
to physical stimuli to attract or repel them away from the soil. Both
these principles have inherent weaknesses and neither has yet produced a universal extraction method. Thus the first which are here
called “mechanical” methods are more especially restricted to certain
groups on account of the great range of density and surface features
found in animals and are particularly inefficient at separating animals
from large quantities of plant matter. On the other hand they work best
in arable soils containing high-proportions of minerals, especially clay,
under which conditions the second type are least efficient. Behaviourtype methods, as we shall call them also tend to be fairly selective and
are useless for removing immobile stages such as eggs and pupae, unless
these are deliberately hatched to a mobile condition. They are, on the
other hand the only available methods for most media containing much
plant matter such as litter and grassland mats.
Considering first the behaviour-type methods it would seem sensi ble
to classify these in terms of the kinds of stimuli such as heat, humidity,
and chemical attractants and repellents used to induce the animals to
leave the soil. However, in practice most practical methods employ a
number of stimuli together and it is more convenient to consider firstly
those methods which operate in the field on untouched soil and secondly
those which are applied in the laboratory to soil or litter sample-units or
cores which have been removed from the habitat.
1. Field Apparatus: Pitf.11 and Baited Traps
Pitfall traps do not necessarily involve the application of specific
stimuli ; frequently they depend simply on chance wanderings of surface
forms. They can be made very simply from glass jam jars or (less suitably) tins and can be left empty or contain a layer of preservative such
as formalin. Many refinements have been described especially from the
Kiel school lead by Tischler (see Heydemann, 1958). In damp climates
it is desirable to arrange a rain-shedding cover and very dilute phenyl
mercuric acetate solution has the advantage over formalin of being non-