SOIL ARTHROPOD SAMPLING
19
of the vial then washed into a smaller tube for storage. Admittedly
this procedure takes more time than the use of alcohol in a tube a t the
bottom of the funnel, but in compensation one is assured of (i) a nonrepellent catching fluid (a large surface of alcohol is distinctly repellent
to some groups; see Macfadyen, 1961), (ii) a fixative fluid of controlled
strength and composition in the storage tubes (according to Gisin the
clegreasing fluid should be replaced by a different fixative solution in
any case) and (iii) the high humidity conditions beneath the sample
which are necessary for efficient extraction.
There remains the question concerning what aqueous medium should
be used in the canisters. The latter must be odourless, non-repellent and
non-volatile, should preferably kill animals falling into it to prevent
predation and escape, should kill moulds which readily attack dead
arthropods and should not corrode the containers. For one or other of
these reasons all the previously used fluids are excluded. A rather unsatisfactory compromise was found in “Agrimycin”, a fungicide which
was advocated in the above paper. Since then a slight repellent effect
has been demonstrated and, more seriously, it has been shown that
earthworms in this solution produce a copious mucus secretion and
undergo autolysis which can make the arthropods very difficult to
separate. Recently Lloyd (see below) has described the use of a picric acid
solution and tests by the present author show that one part saturated
picric acid to one part water has no detectable repellent effect and
completely fixes all animal tissues. The yellow staining may sometimes
be a disadvantage in the determining of new material, but at present
this appears to be the best medium available. Tests on further possible
substances are continuing.
A new device for extracting arthropods from leaf-litter has recently
been developed a t the Bureau of Animal Population, Department of
Zoological Field Studies, Oxford University, by Denys Kempson, Monte
Lloyd and Raymond Ghelardi. (A detailed report for publication is in
preparation, but the following brief note has been authorized for inclusion in the present article.) Each sample is suspended a short distance
above an aqueous solution of picric acid contained in a straight-sided
closed vessel. The collecting vessels are immersed in a circulating cool
water-baththat is well insulated from the infra-red heat source above the
samples. A battery of infra-red bulbs switches on and off in alternation
with conventional light bulbs, producing an adjustable pattern of heat
pulses with continuous light. A high humidity is present directly under
the sample from the beginning. The extraction process requires about
a week, during which time very high gradients of both humidity and
temperature are established through the samples. Extraction efficiencies
have been determined by soaking and hand-sorting the dried residue
19
of the vial then washed into a smaller tube for storage. Admittedly
this procedure takes more time than the use of alcohol in a tube a t the
bottom of the funnel, but in compensation one is assured of (i) a nonrepellent catching fluid (a large surface of alcohol is distinctly repellent
to some groups; see Macfadyen, 1961), (ii) a fixative fluid of controlled
strength and composition in the storage tubes (according to Gisin the
clegreasing fluid should be replaced by a different fixative solution in
any case) and (iii) the high humidity conditions beneath the sample
which are necessary for efficient extraction.
There remains the question concerning what aqueous medium should
be used in the canisters. The latter must be odourless, non-repellent and
non-volatile, should preferably kill animals falling into it to prevent
predation and escape, should kill moulds which readily attack dead
arthropods and should not corrode the containers. For one or other of
these reasons all the previously used fluids are excluded. A rather unsatisfactory compromise was found in “Agrimycin”, a fungicide which
was advocated in the above paper. Since then a slight repellent effect
has been demonstrated and, more seriously, it has been shown that
earthworms in this solution produce a copious mucus secretion and
undergo autolysis which can make the arthropods very difficult to
separate. Recently Lloyd (see below) has described the use of a picric acid
solution and tests by the present author show that one part saturated
picric acid to one part water has no detectable repellent effect and
completely fixes all animal tissues. The yellow staining may sometimes
be a disadvantage in the determining of new material, but at present
this appears to be the best medium available. Tests on further possible
substances are continuing.
A new device for extracting arthropods from leaf-litter has recently
been developed a t the Bureau of Animal Population, Department of
Zoological Field Studies, Oxford University, by Denys Kempson, Monte
Lloyd and Raymond Ghelardi. (A detailed report for publication is in
preparation, but the following brief note has been authorized for inclusion in the present article.) Each sample is suspended a short distance
above an aqueous solution of picric acid contained in a straight-sided
closed vessel. The collecting vessels are immersed in a circulating cool
water-baththat is well insulated from the infra-red heat source above the
samples. A battery of infra-red bulbs switches on and off in alternation
with conventional light bulbs, producing an adjustable pattern of heat
pulses with continuous light. A high humidity is present directly under
the sample from the beginning. The extraction process requires about
a week, during which time very high gradients of both humidity and
temperature are established through the samples. Extraction efficiencies
have been determined by soaking and hand-sorting the dried residue