Defensive Symbionts in Aphids and Other Insects
Symbiotic associations with microorganisms are ubiquitous in invertebrates, occurring in many phyla in both marine and terrestrial habitats. In terrestrial arthropods, the microorganisms are often heritable, being passed from mother to offspring with high delity (Buchner, 1965). Inherited symbiosis is particularly common in insects and most often involves an association with bacteria. Recent results indicate that some heritable symbionts in insects protect hosts from natural enemies. In this chapter, we brie y review the general phenomenon of heritable symbiosis in insects and summarize the results on cases in which these symbionts provide defenses. Although symbiont-based protection has been examined most extensively in aphids, the phenomenon is potentially common across many insect groups.