Notes on Methods for the Extraction of Small Soil Arthropods

Although methods for the extraction of soil animals vary much in detail they all owe their origin in principle to methods of hand sorting or to two devices developed by Berlese; the 'Berlese funnel' was invented by him in about 1895 (Berlese 1905), and so, also, was a simple flotation device described by Balogh (1948). Neither method was originally intended to extract all the animals with full quantitative efficiency, and it is in attempting to make them do this that the many subsequent variations in technique have been developed. To-day the two fundamentally distinct types of method remain, each with its devotees and its critics, and we still have no statistically valid published data on the relative efficiencies of the different methods. One conclusion, which is inescapable from the published work, is that there is no universal extraction method which can be used for all soils and all groups of animals, and therefore methods must be adapted to the particular conditions of any particular study. The following notes include some approximate comparisons of methods which are published now in the hope that they will save other workers from repeating unnecessary preliminary work. As far as possible definite problems which still need clarification are stressed, but it should be emphasized that these notes refer specifically to micro-arthropods, mites and Collembola in a size-range from about 0-1 to 5-0 mm. length. It is hoped to publish later further notes on the extraction of larger arthropods.