The abundance of the larvae of Phyllobius piri L. and P. viridicollis F. (Col. Curculionidae) was investigated in an abandoned field in central Sweden. On the basis of the individual growth curve and the life table of the larvae the production of P. piri was calculated to be 4.6 ± I.9 g dw per m2 or 25 ± II kcal per m2 (mean ± 95 per cent c.i.). The population of the hibernating pupae of P. piri was about 500 per m2 during three successive years. During the same period the abundance of hibernating larvae of P. viridicollis was I00-250 per m2. Notes are given on the life history of the two species. The larvae are described by B. Lekander in an appendix.