The Abundance and Diversity of the Beetle Fauna of Grass Tussocks

The occurrence of Coleoptera in grass tussocks has been known to beetle collectors for many years. Pearce (1948) suggested that the invertebrate fauna of tussocks might be an interesting ecological study, and pointed out that the Coleoptera were one of the best represented orders of insects. As the numbers were highest in the winter, he also suggested that the tussocks might provide shelter from cold, an idea which had been put forward earlier by Hancock (1923) and Holmquist (1926). Little quantitative work has been done on the fauna of tussocks as such, although Richards (1926), Ford (1937, 1938), Pearce (1948) and Macfadyen (1952) all give data on some insects which occur in tussocks of various grasses. The possible shelter from climatic extremes given by tussocks has also received little attention, although Ford (1937) made brief measurements of temperature and humidity in Bromus tussocks, and suggested that their high humidity was of vital importance to their fauna; protection from drought was demonstrated by Clark (1947) in New South Wales, and Madge (1953) showed that tussocks prevented larvae of the moth Oncopera from drowning when the soil was water-logged in winter. The beetles of grass tussocks were studied from 1961 to 1964 at the Imperial College Field Station, Silwood Park, Berkshire, to obtain data on their numbers and on the possible roles which this microhabitat plays in their survival, especially during cold conditions. This paper gives the results of work on the numbers of beetles occurring in tussocks, and the life histories of selected common species. Microclimatic conditions in tussocks were also measured (Luff 1965a). Experiments were then carried out on the previously selected species to assess the possible importance of the shelter given by the tussocks; the results of these will be published later.