14
A. MACFADYEN
satisfactory cores by sinking a plastic ring into the ground with the aid
of a carpenter’s chisel. A disadvantage of any system which uses rings
of fixed depths is that natural boundaries of the soil profile are ignored
and any vertical separation which is done by cutting the soil core at the
ring junctions is quite arbitrary. This difficulty is overcome by O’Connor
(1957) in his longitudinally split sampling tool. It has been argued that
serious losses can result from compression caused by the use of core
samplers (Murphy, 1958) but there does not appear to be any quantitative evidence for such an effect in the case of the type of sampler just
described. It does appear, on the other hand, that manipulation of the
soil core by hand can lead to reduced yields (Macfadyen, 1953) and doubtless losses would occur if the soil were seriously compressed. Most workers
now agree that an intact soil core yields more animals than a teasedout one and that a core from near the surface should be inverted when
placed in the funnel-type extractor so that surface living animals with
limited digging powers can easily make their way out (Macfadyen, 1953).
i. Wet Funnel Methods. These are suitable for extracting animals
which normally live in the water films of the soil and have been widely
- and successfully used for such groups as nematodes, enchytraeid
worms and rotifers (e.g. Nielsen, 1948; Peachey, 1959 ; O’Connor, 1955).
Among the arthropods only the Tardigrada are water film dwellers and
they can certainly be obtained in large numbers from moss and similar
media by means of the Baermann funnel. This is simply a glass funnel
fitted with a pinch cock below and a wire gauze some distance below the
rim. A sample is placed on the centre of the gauze leaving a clear annulus
round the edge and the whole is flooded with water and placed beneath
an electric bulb of such a wattage that the temperature of the water near
the sample rises to about 40” C in two hours. As the temperature rises
aquatic animals swim actively into the water and then succumb to the
higher temperature and sink to the stem of the funnel. After about
twelve hours the pinch cock is opened for long enough to draw off abcut
a quarter of the contents of the funnel. The process can be repeated.
An inverted wet “funnel” method in which the animals move upward from warm to cold temperatures and into LL layer of sand, from
which they are removed by simple flotation has been used for enchytraeids (Nielsen, 1953) but not for soil arthropods ; conceivably it
could be of value for collecting small semi-aquatic crustacea such as
harpactids, which occur in certain soils.
ii. Dry Funnel Methods. For fuller accounts of the history of these
methods see Heydemann (1958) and Macfadyen (1953).
Berlese (1905) was the &st biologist to use heat in conjunction with a
funnel for collecting small arthropods. He used a water jacket round the
funnel and the sample was suspended near the top so that it was dried
A. MACFADYEN
satisfactory cores by sinking a plastic ring into the ground with the aid
of a carpenter’s chisel. A disadvantage of any system which uses rings
of fixed depths is that natural boundaries of the soil profile are ignored
and any vertical separation which is done by cutting the soil core at the
ring junctions is quite arbitrary. This difficulty is overcome by O’Connor
(1957) in his longitudinally split sampling tool. It has been argued that
serious losses can result from compression caused by the use of core
samplers (Murphy, 1958) but there does not appear to be any quantitative evidence for such an effect in the case of the type of sampler just
described. It does appear, on the other hand, that manipulation of the
soil core by hand can lead to reduced yields (Macfadyen, 1953) and doubtless losses would occur if the soil were seriously compressed. Most workers
now agree that an intact soil core yields more animals than a teasedout one and that a core from near the surface should be inverted when
placed in the funnel-type extractor so that surface living animals with
limited digging powers can easily make their way out (Macfadyen, 1953).
i. Wet Funnel Methods. These are suitable for extracting animals
which normally live in the water films of the soil and have been widely
- and successfully used for such groups as nematodes, enchytraeid
worms and rotifers (e.g. Nielsen, 1948; Peachey, 1959 ; O’Connor, 1955).
Among the arthropods only the Tardigrada are water film dwellers and
they can certainly be obtained in large numbers from moss and similar
media by means of the Baermann funnel. This is simply a glass funnel
fitted with a pinch cock below and a wire gauze some distance below the
rim. A sample is placed on the centre of the gauze leaving a clear annulus
round the edge and the whole is flooded with water and placed beneath
an electric bulb of such a wattage that the temperature of the water near
the sample rises to about 40” C in two hours. As the temperature rises
aquatic animals swim actively into the water and then succumb to the
higher temperature and sink to the stem of the funnel. After about
twelve hours the pinch cock is opened for long enough to draw off abcut
a quarter of the contents of the funnel. The process can be repeated.
An inverted wet “funnel” method in which the animals move upward from warm to cold temperatures and into LL layer of sand, from
which they are removed by simple flotation has been used for enchytraeids (Nielsen, 1953) but not for soil arthropods ; conceivably it
could be of value for collecting small semi-aquatic crustacea such as
harpactids, which occur in certain soils.
ii. Dry Funnel Methods. For fuller accounts of the history of these
methods see Heydemann (1958) and Macfadyen (1953).
Berlese (1905) was the &st biologist to use heat in conjunction with a
funnel for collecting small arthropods. He used a water jacket round the
funnel and the sample was suspended near the top so that it was dried