UTTAR PRADESH JOURNAL OF ZOOLOGY

Arthropods constitute the most diverse animal phylum on Earth, and the majority of their species pass through a metamorphic life cycle in which temperature, moisture and photoperiod govern the timing of moulting, pupation and reproductive maturation. Anthropogenic climate change is altering each of these cues simultaneously, with consequences that extend from individual development to population persistence. This review synthesises evidence on how rising mean temperatures, more frequent heatwaves, shifting precipitation regimes and ocean warming and acidification affect metamorphic development, voltinism, diapause, body size, fecundity and sex allocation across insects, crustaceans, arachnids and myriapods. Warming generally accelerates larval and nymphal development up to a thermal optimum, beyond which performance declines sharply, producing smaller adults through the temperature–size rule, altered generation number, and disrupted synchrony between diapause induction and seasonal cues. Reproductive consequences include shifts in fecundity, mating phenology, sperm viability under heat stress and, in some taxa, skewed offspring sex ratios. Marine and freshwater crustaceans show parallel sensitivity of larval moulting and embryo development to warming and acidification, while terrestrial arthropods face compounding effects of drought and altered host-plant or prey phenology. The review identifies marked taxonomic and geographic unevenness in the evidence base, a shortage of multigenerational and multifactorial experiments, and limited integration between physiological and population-level models. Future research priorities include long-term field monitoring of voltinism shifts, experiments combining thermal and hydric stressors, and trait-based forecasting frameworks capable of informing conservation and pest management policy under projected warming scenarios.