Insects and Their Chemistry

Abstract

This chapter begins with an introduction to some biological and chemical aspects of insects. The general structure of insect bodies is shown, including the chemical composition of chitin composing the insects’ exoskeleton. Insects release highly specific pheromones to communicate between individuals of the same species and to induce specific biological responses from fellow insects. Structures of characteristic pheromones are shown, like bombykol from the silkworm moth and aggregation pheromones of bark beetles. In contrast to most plant colors, many insect colors are the result of physical structures; they can also be the result of pigments. Some of their chemical structures, like the pterins in butterfly wings, are shown. Some beetles attract mates or lure prey with timed emission of light flashes, known as bioluminescence. The bioluminescent compound is luciferin which in an enzyme-catalyzed reaction sequence releases energy in the form of light. Defensive chemical compounds in insects may be in the form of sharp scents or of irritating, toxic sprays. The defensive compounds range from simple molecules like hydrogen cyanide or formic acid to compounds with more complex molecular structures, including terpenes and steroids. Some insects directly use defensive plant compounds, most of them with complex chemical structures, in their own defense. Hormones regulate many physiological processes in the bodies of insects. There are three major classes of insect hormones: the neurohormones, the juvenile hormones, and the molting hormones.