S O I L A R T H R O P O D S A M P L I N G
11
special vessels are required. An ofice-type tape recorder, operated by a
foot pedal, can be an invaluable aid in counting because one's hands are
free to manipulate the microscope and forceps and eye-strain due to
constantly looking up from the microscope is reduced. When played
back the numbers of each species can be counted either on paper or with
the aid of a multiple abacus.
All these devices result in economy of counting effort but it should be
stressed once more that complete counts should only be employed when
the nature of the study renders them essential.
I\'. A SURVEY OF AVAILABLE EXAMINATION A N D
SEPARATION PROCESSES
The aim of this section is not to describe complete sampling techniques for all possible situations but to discuss under three main and a
number of subsidiary headings the main principles which have been
employed in attempting to examine or extract soil arthropods. Some
examples of the application of each principle, including practical details,
then follow and finally a discussion of the inherent advantages and limitations of the employment of this particular principle.
A. THE E X A M I N A T I O N O F S O I L WITH A N I M A L S I N S I T U
Despite its ready availability soil is a remote medium for the biologist
to study and many attempts have been made to look inside the soil and
see what animals are doing there. Kubiena (1938) introduced special
microscopic apparatus for use in the field, but this has not been widely
adopted and the most successful work of this nature has resulted from
soil sectioning. Haarlerv and Weis-Fogh (1953) developed a method of
sectioning soil cores which had been impregnated with agar after the
cores had been first frozen in solid carbon dioxide and then fixed in
formalin vapour. I n this way considerable insight was gained into the
feeding behaviour of small arthropods and also into the distribution of
animals of different size groups in relation to soil pore size. A different
approach to the same problem is that, of Alexander and Jackson (1955)
who used resin impregnation followed by a grinding technique similar to
the methods used by geologists. The Haarlrav technique uses simple
apparatus and has provided biological information which could not
otherwise have readily been obtained : it is however rather laborious and
largely limited to commoner species. More recently however Tribe (1960,
1961) has obtained somewhat similar results as a side product of work
on microbial decomposition of cellulose. The cellulose was attached to
glass slides which were buried and then dug up for examination at intervals. Especially in the later stages oribatid mites as well as nematodes
were found feeding on micro-organisms and it seems likely that a re-
11
special vessels are required. An ofice-type tape recorder, operated by a
foot pedal, can be an invaluable aid in counting because one's hands are
free to manipulate the microscope and forceps and eye-strain due to
constantly looking up from the microscope is reduced. When played
back the numbers of each species can be counted either on paper or with
the aid of a multiple abacus.
All these devices result in economy of counting effort but it should be
stressed once more that complete counts should only be employed when
the nature of the study renders them essential.
I\'. A SURVEY OF AVAILABLE EXAMINATION A N D
SEPARATION PROCESSES
The aim of this section is not to describe complete sampling techniques for all possible situations but to discuss under three main and a
number of subsidiary headings the main principles which have been
employed in attempting to examine or extract soil arthropods. Some
examples of the application of each principle, including practical details,
then follow and finally a discussion of the inherent advantages and limitations of the employment of this particular principle.
A. THE E X A M I N A T I O N O F S O I L WITH A N I M A L S I N S I T U
Despite its ready availability soil is a remote medium for the biologist
to study and many attempts have been made to look inside the soil and
see what animals are doing there. Kubiena (1938) introduced special
microscopic apparatus for use in the field, but this has not been widely
adopted and the most successful work of this nature has resulted from
soil sectioning. Haarlerv and Weis-Fogh (1953) developed a method of
sectioning soil cores which had been impregnated with agar after the
cores had been first frozen in solid carbon dioxide and then fixed in
formalin vapour. I n this way considerable insight was gained into the
feeding behaviour of small arthropods and also into the distribution of
animals of different size groups in relation to soil pore size. A different
approach to the same problem is that, of Alexander and Jackson (1955)
who used resin impregnation followed by a grinding technique similar to
the methods used by geologists. The Haarlrav technique uses simple
apparatus and has provided biological information which could not
otherwise have readily been obtained : it is however rather laborious and
largely limited to commoner species. More recently however Tribe (1960,
1961) has obtained somewhat similar results as a side product of work
on microbial decomposition of cellulose. The cellulose was attached to
glass slides which were buried and then dug up for examination at intervals. Especially in the later stages oribatid mites as well as nematodes
were found feeding on micro-organisms and it seems likely that a re-