The Bionomics of Lema melanopa, L. (Criocerinae), in Great Britain

Abstract

The beetle, Lema melanopa, is a serious pest of cereal crops in certain areas of Europe and is becoming increasingly common on cereals in Britain. A survey of the literature indicates that the life-history differs in various localities, and no previous account has been given of the life-history in this country.The life-cycle in Britain is briefly as follows. The adult beetles emerge from hibernation in April, mate and commence to oviposit towards the end of May. Oviposition continues for nearly two months, and adults commence to emerge early in July and continue to do so until September. There is no indication that a second brood occurs, although the climate would permit of one.The adults feed freely after emergence, but largely on grasses, prior to hibernating in November. In the spring they feed almost exclusively on the leaves of young cereals. The larvae feed principally on cereals. Adults tend to be gregarious and are very long-lived, numbers living over a second winter.Two larval parasites occur in Britain and further information concerning these is being obtained. Of all larvae collected in the field 25 per cent. were found to be parasitised.The loss of crop sustained as a result of attack by this pest amounts on the Continent, in extreme cases, to as much as 50 per cent. of the total. Control measures consist of cultural methods, spraying and dusting. Certain of these might be adapted for use in this country with reasonable hope of success.