Introduction

Abstract

Aphids have fascinated and frustrated man for a very long time. This is mainly because of their intricate life cycles and close association with their host plants, their polyphenism, and their ability to reproduce both asexu-ally and sexually. Thus aphids are ideal for studying many of the topical issues in ecology. The term ‘ecology’ is used here in a broad sense to include aspects of the functional biology of the group necessary for an understanding of the population and community levels of organization. The modes of feeding and reproduction that developed early in aphid evolutionary history led to a close and specific association with certain plants, and affected aphid size and population structure. In turn, these consequences have influenced aphid life-history patterns, dispersal behaviour, population dynamics, species diversity and world-wide distribution.