MORPH IDENTIFICATION IN NATURAL-POPULATIONS OF ALATE FEMALE BIRD CHERRY APHIDS, RHOPALOSIPHUM-PADI L, BY MULTIVARIATE METHODS

A discriminant analysis was done to determine which morphological char acteristics contributed most to the identification of alate female mor phs of Rhopalosiphum padi in natural populations collected from either Prunus padus or in suction traps. Twenty two characters were measured or counted, including wing dimensions, and three ratios were included . Analyses were done to separate morphs that might occur naturally tog ether, i.e. emigrants and 'early' exules, or 'late' exules and gynopar ae. Emigrants were distinguished readily from early exules, but gynopa rae were not so easily separated from late exules. The biological sign ificance of the morphological: differences between morphs and the prac tical implications of being able to identify the different morphs are discussed.