AbstractInvertebrate numbers were studied in two white clover cultivars trials, grown with perennial ryegrass Weevils (Sitonaspp.), slugs, lucerne flea, leatherjackets and as were more common (at least at some life stage) in cultivars of lower cyanogenic potential. Damage to clover foliage by the first three species was also negatively related to cyanogenesis. The production of HCN ranged from 0.025 mg to about 1.8 mg g−1fresh leaf. There was no evidence of any other factor influencing cultivar preference.Cyanogenesis had most effect on numbers of weevil larvae and leatherjackets. The effect on weevil larvae was attributed partly to intercultivar differences in oviposition, but it was also suspected that larvae had fed on cyanogenic parts of the plant before reaching the root. Leatherjacket numbers developed inter‐cultivar differences during larval growth. In one case these differences were detectable by December. By March in the second experiment there were approximately three times as many leatherjackets at the low as at the high end of the cyanogenic range. Approximately four times as manySitona larvaewere found at the lower as at the higher end of the scale. There was some evidence that a higher clover content in the sward was attractive to ovipositingTipula paludosabut not in recently harvested cultivars of high cyanogenic poten