EFFECT OF CLIMATE ON THE PROPORTION OF MALES IN THE AUTUMN FLIGHT OF THE APHID RHOPALOSIPHUM-PADI L. (HOM., APHIDIDAE)

The composition of autumn flights of a cereal pest aphid, Rhopalosiphu m padi, was studied in relation to climate. At 10 sites in France and at Rothamsted and Starcross (UK), evidence was sought for a relationsh ip between winter temperature and the proportion of males. By calculat ing Goldwin's correlogram, significant correlations were detected betw een cold periods in the early winter and the proportions of males at t he five mildest sites, suggesting an effect of temperature on the bala nce between holocyclic and non-holocyclic clones. The five sites where no significant correlations were detected are generally cold in winte r, and are likely to be largely dominated by holocyclic clones. The te mperature in late summer/early autumn may also have an effect on the p roportion of males.