Chemical Defense

This chapter discusses chemical defense, which is the ability of insects to biosynthesize a large variety of compounds for use as agents of chemical defense against their omnipresent enemies. Many of these compounds are unique products with diverse modes of toxicity against a variety of vertebrate and invertebrate predators. These defensive secretions often originate from unlikely sources that appear to optimize the effectiveness of the chemical defensive systems. Ultimately, for countless species of insects, chemical defense and survival are synonymous. For example, the proteinaceous saliva of the hemipteran Vela capraii has been adapted to promote escape from potential predators in aquatic environments. This aquatic true bug will discharge its saliva onto the water surface, a reaction that results in lowering the surface tension of the water behind the bug and propelling it across the aquatic surface. There are other defensive techniques as well such as froths from diverse glands, nonsalivary entangling secretions, externalizing allomones by reflex bleeding, blood as part of a glandular secretion, and nonglandular discharges of plant origin.