Desiccation tolerance in insects is frequently treated as a single physiological phenotype, although survival under water deficit can arise from fundamentally different mechanisms. Some insects primarily restrict water loss through the cuticle, respiratory system and excretory organs, whereas others tolerate substantial dehydration through osmotic adjustment, metabolic suppression and cellular protection. At the extreme, anhydrobiotic chironomids reorganize metabolism and stress signaling sufficiently to survive near-complete water loss. This integrative review examines how these levels interact without assuming that molecular responses observed in one taxon, life stage or dehydration regime represent universal mechanisms. Evidence is organized across cuticular and respiratory water loss, epithelial ion and water transport, compatible-solute metabolism, stress signaling, proteostasis, membrane protection and oxidative damage–repair processes. The synthesis distinguishes mechanisms that reduce the rate of dehydration from those that preserve function after water has already been lost. It further proposes that desiccation tolerance is best interpreted as a coordinated state transition in which water conservation, solute redistribution, metabolic demand, protective macromolecules and recovery capacity become limiting at different stages of dehydration and rehydration. This framework clarifies why transcriptomic induction alone cannot demonstrate protection and why extreme anhydrobiosis should not be generalized to ordinary insect drought resistance.
