A NEW APPARATUS FOR SEPARATING INSECTS AND OTHER ARTHROPODS FROM THE SOIL

Abstract

SUMMARY The published methods for the separation of insects and other animals from the soil are briefly described. None of these methods being sufficiently rapid or efficient for soil fumigation investigations, a new method has been devised. The principle of the method is flotation by a dense liquid (a solution of magnesium sulphate sp. gr. 1.11) aided by stirring of the soil and a stream of fine air bubbles passing from the bottom upwards through the mixture of soil and solution. This produces a froth which contains all the animals, and by raising the level of the liquid in the cylinder the froth is swept over into a tank filled with magnesium sulphate solution; here is deposited any soil that has been carried over. The clear solution is then passed on to a Buchner funnel where the insects and other animals are retained. A black filter paper is used in order to show up Collembola and other colourless organisms. The apparatus has many advantages: Rapidity. The separation taking 30–40 min. from taking the soil sample of 6–7 lb. weight. Cleanliness. The operation can be carried out in an ordinary laboratory. Efficiency. All the organisms are concentrated in a small volume of residue, less than 1 per cent of the original soil, and are undamaged. Non‐toxicity. The great majority of the insects come through alive, so that eggs and larvae may be bred out for purposes of identification. A full account is given of the technique employed. The solution may be used again and again as the clay settles very quickly and the clear liquid may be syphoned or poured off. Very high figures have been obtained for the soil population. These are much in excess of those recorded by most other workers with agricultural soils; for example, from fallow land 60‐6 million animals per acre were recorded and from new grass land, 121‐4 million per acre.1