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Examines the effect of climate on the proportion of males in the autumn flight of aphid Rhopalosiphum padi in Great Britain. Reproduction of anholocycly; Composition of the autumn flights of cereal pest aphid; Factors affecting the geographical distribution of males.

The stylet penetration activities of Sitobion avenae F. were followed with an electronic method (DC-EPG) on resistant and susceptible wheat genotypes. Discriminant analysis was therefore applied to data evaluated on each electrical penetration graphs obtained (EPGs). The variables which mostly explained the resistance-susceptibility status of the wheat genotypes appeared to be related to the ingestion sap event (as represented by pattern E2), either to the time preceding first occurrence of a sap ingestion event or to the total time spent by the aphid ingesting sap from the sieve elements of the phloem. On the basis of their stylet penetration activities, individuals were separated into three blocks. The first one was made up the individuals tested on susceptible or slightly resistant wheat ('susceptible block'). The second one contained the individuals tested on two resistant genotypes ('resistant block l') and the third one regrouped the individuals tested on another resistant genotype ('resistant block 2'). These results are discussed in relation to the possible mechanisms of wheat resistance to S. avenae. [ABSTRACT FROM AUTHOR]