Observations on the natural mortality of the overwintering pupa of the cabbage root fly, Delia brassicae (Wiedemann), in Ireland

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Abstract
SUMMARY: The mean winter loss of pupae in four cabbage root fly populations in two peatland sites in Ireland in 1971/72, 1974/75 and 1975/76 was 58 · 4 per cent. Predation by carabids may have been involved as pupal loss was associated, in three winters, with the abundance of either Nebria brevicollis (F.) adults or carabid larvae. The parasites Trybliographa rapae (Westw.) (Hymenoptera: Cynipidae) and Aleochara bilineata Gyll. (Coleoptera: Staphylinidae) were recorded at average rates of 10·4 and 3·9 per cent respectively.