Developmental plasticity is often interpreted as an anticipatory adjustment through which early environmental conditions prepare insects for later life. That interpretation is stronger than the observation that developmental environments alter adult phenotypes. For plasticity to function specifically as environmental forecasting, an early-life cue must contain reliable information about a later selective environment, the induced response must persist to the relevant adult stage, its developmental costs must not outweigh subsequent benefits, and adult performance must improve under the condition predicted by the cue. This perspective develops a proposed Cue-Predictiveness Framework that separates these requirements and identifies where forecasting interpretations succeed or fail. Evidence from insect thermal plasticity, photoperiodic polyphenism, coloration, dispersal morphology, physiology, reproduction, and behavior shows that early environments can strongly alter later phenotypes, but these effects are frequently genotype-dependent, trait-specific, reversible, costly, or disconnected from adult fitness. Environmental predictability is therefore treated as a property of cue–future-environment relationships rather than of plastic responses themselves. Full developmental-by-adult environmental comparisons further show that matching environments do not consistently maximize reproductive performance and that developmental optima or persistent developmental damage can provide alternative explanations. The framework consequently distinguishes cue responsiveness, developmental carry-over, adult environmental match, and adaptive forecasting as progressively stronger inferential claims. It predicts that forecasting should be most defensible where cue reliability is high, developmental responses persist to the relevant adult context, response costs remain limited, and matched-environment performance advantages are directly demonstrated.
