Biol. Rev.(), , pp. – Printed in Great Britain SPATIAL FLOWER PARAMETERS AND INSECT SPATIAL VISION B A. DAFNI, M. LEHRER P. G. KEVAN Institute of Evolution, Haifa University, Haifa , Israel Zoologisches Institut der Universita t Zu rich, Winterthurerstrasse , CH-, Zu rich, Switzerland Department of Environmental Biology, University of Guelph, Guelph, Ontario NG W, Canada (Received January ; revised May ; accepted June ) ABSTRACT The present article reviews recent and older literature on the spatial parameters that flowers display, as well as on the capacities of anthophilous insects to perceive and use these parameters for optimizing their foraging success. Although co-evolution of plants and pollinators has frequently been discussed with respect to floral colours and insect colour vision, it has rarely been assessed with respect to insect spatial vision and spatial floral cues, such as shape, pattern, size, contrast, symmetry, spatial frequency, contour density and orientation of contours. This review is an attempt to fill this gap. From experimental findings and observations on both flowers and insects, we arrive at the conclusion that all of the spatial and spatio-temporal parameters that flowers offer are relevant to the foraging task and are tuned to the insect’s visual capacities and visually guided behaviour. We try, in addition, to indicate that temporal cues are closely related to spatial cues, and must therefore be included when flower–pollinator interactions are examined. We include results that show that colour vision and spatial vision have diverged over the course of evolution, particularly regarding the processing of spatio-temporal information, but that colour vision plays a role in the processing of spatial cues that are independent of temporal parameters. By presenting this review we hope to contribute to closer collaboration among scientists working in the vast fields of botany, ecology, evolution, ethology and sensory physiology. Key words : floral spatial parameters, insect spatial vision, flower–pollinator interactions, visually guided behaviour, co-evolution. CONTENTS I. Introduction . . . . . . . . . . . . . . . II. The flower as a functional unit and the insect pollination syndrome . . . . () Attraction units and pollination units . . . . . . . . . (a) Inflorescences . . . . . . . . . . . . . (b) Patches . . . . . . . . . . . . . . () Flower competition and the pollination syndromes . . . . . . . (a) Competitive advertisement and discovery advertisement . . . . . (b) The pollination syndrome . . . . . . . . . . . III. Flower size and insect visual acuity . . . . . . . . . . () The role of the size of the attraction unit : experimental data . . . . . () Side advertisement . . . . . . . . . . . . . () Insect spatial acuity . . . . . . . . . . . . . (a) The compromise between sampling density and contrast sensitivity . . . (b) Intensity contrast and colour contrast . . . . . . . .