Developmental environments can influence insect phenotypes long after the exposure itself has ended, yet persistence across metamorphosis is neither inevitable nor uniform among traits. This systematic review examines how juvenile nutritional, thermal, microbial, toxicological, competitive, and other environmental conditions translate into persistent effects, compensation, reversal, or delayed costs at later life stages. The review distinguished immediate developmental responses from cross-stage outcomes and classified later phenotypes according to whether an earlier effect persisted, was buffered, disappeared, changed direction, or re-emerged in a different fitness-related trait. The systematic search yielded 32 eligible primary studies after deduplication and staged screening. Across the evidence base, adult body size, physiology, immunity, reproductive performance, longevity, and behavior frequently responded differently to the same developmental exposure. Apparent normalization of development time or size therefore did not reliably indicate whole-organism recovery. Conversely, persistent juvenile effects were sometimes restricted to particular sexes, phenologies, adult environments, or outcome classes. We propose a trajectory-based interpretation in which carry-over, compensation, reversal, and hidden cost are treated as analytically separate cross-stage states. This approach avoids equating metamorphic persistence with mechanism, phenotypic compensation with fitness recovery, or adult trait change with adaptive benefit.
