THE RELATIVE IMPORTANCE OF MOLLUSCS AND INSECTS AS SELECTIVE GRAZERS OF ACYANOGENIC WHITE CLOVER (TRIFOLIUM REPENS)

Selective grazing of acyanogenic and cyanogenic white cloverwas investigated by a field experiment using biocides to maintain(a) mollusc only, (b) insect only, (c) both mollusc and insect,and (d) neither mollusc nor insect, grazing regimes. Molluscsfed more on acyanogenic clover throughout the year, whereasinsects damaged more acyanogenic plants in late summer, butmore cyanogenic plants in spring. When both molluscs and insectswere present, the net effect was greater damage to acyanogenicplants. However, in situations where insects are more abundantthan molluscs there might be a net selection against cyanogenicclover. (Received 16 December 1988; accepted 22 February 1989)