Dung is best incubated in a light place, for example on a table in a warm room, on layers of moist filter paper or other absorbent material. For rabbit pellets, and samples of similar size, Petri dishes are ideal; for horse 'apples', and larger types of dung, large covered dishes such as glass casseroles, plastic sandwich boxes or yoghurt pots are needed. The top third cut from a plastic lemonade or mineral water bottle fits neatly in a Petri dish, and replacing the screw cap with a cotton wool plug allows aeration and gives adequate height for developing basidiomycetes. Samples should not be kept in airtight containers for any length of time after collection, as in such conditions insects and nematodes tend to break down the dung, and anaerobic conditions which do not favour the fungi rapidly develop. If they cannot be set to incubate soon after collection they can be gently air dried, as most dung fungi will remain alive after such treatment and grow out when the sample is eventually moistened. The absorbent material should be kept moist. Although free water will not allow the best development of ascomycetes, the succession of basidiomycetes appears to vary with the wetness of the dung. Earthworms and insect larvae should be excluded from the samples as far as possible, for they break up the dung too much; activity of the latter can be reduced by spraying lightly with a household insecticide. If space is limited and cultures are kept nearby, it is very important to prevent mite infestation. Containers can be isolated by placing on glass plates lightly smeared with Vaseline, to which an acaricide (e.g. methyl benzoate) can be added.