The Insects

Introduction

Insects generate a spectacular variety of visual signals, from multicolored wing patterns of butterflies, through metallic-shiny beetles to highly contrasting warning coloration of stinging insects and their defenseless mimics. Section 25.1 explains what colors are and the subsequent sections describe how insect colors result from a variety of physical structures (Section 25.2) and pigments (Section 25.3). Often, several pigments are present together, and the observed color depends on the relative abundance and positions of the pigments, as well as control signals generating color patterns during development (Section 25.4). The position of color-producing molecules relative to other structures is also important, and this may change, resulting in changes in coloration (Section 25.5). The many biological functions of color in insect signaling are covered in Section 25.6. Table 25.1 lists the sources of color in some insect groups. A small selection of insects also exhibits fluorescence or luminescence (Section 25.7).

The nature of color

Color is not an inherent property of objects; it is a perceptual attribute that depends on illumination, the spectral reflectance of an object and its surroundings, as well as the spectral receptor types and further neural processing in the animal in question. Thus the same object might appear differently colored to different viewing organisms. A red poppy, for example, is red to human observers, but appears as a UV-reflecting object to a bee pollinator, which does not have a red receptor and, like all insects studied to date, sees UV-A light between 300 nm and 400 nm. For reasons of simplicity, the color terminology in this chapter specifies what a human observer will perceive under daylight conditions. Information about UV is provided separately where available.