Factors determining the distribution of sycamore aphids on sycamore leaves during summer

Abstract1 In summer the sycamore aphid's responses to gravity, light direction and intensity and unidentified features of a leaf's surface result in the aphid settling and feeding on the undersurface of leaves. 2 At this time the petioles are a poor source of food and are not colonized. 3 Removal of leaf laminae results in premature abscission of the petioles. Prior to abscission the petioles become senescent and a richer food source than the laminae of mature leaves, and are colonized by aphids.