Physiological and Biochemical Mechanisms of Insect Color Change Towards Understanding Molecular Links

Insect color patterns are prominently diverse, serving significant physiological and ecological functions. However, the environments surrounding insects are not always constant, complicating attempts to set the most suitable color pattern as a fixed phenotype. While not ubiquitous, many insects possess a sophisticated mechanism that adjusts their surface color in response to external cues to cope with such variable environments. Compared with other well-known color changing-animals like vertebrates and aquatic invertebrates, insects face the challenge of flexible color change because they lack chromatophores like vertebrates but have a melanized exoskeleton. Instead, a variety of unique processes have been adopted in a wide range of insects. This chapter outlines the diverse mechanisms underlying various insect color changes by introducing physiological and biochemical research results and recent progress in molecular studies. Here, the term color change is considered in a broad sense; it covers not only color changes that take place within the life of a single insect, but also alternative color morphs resulting from adaptive developmental plasticity. This review highlights that ecologically relevant color changes are achieved by an elaborate system that requires the coordination of several dedicated pieces of machinery, including variable architectures, perception and integration systems for environmental cues, neuroendocrine signaling systems, and color-generating apparatuses.