Body size is a critical trait shaping ectotherm thermal tolerance, yet how body size mediates thermal acclimation remains poorly understood in insects. Here, we conducted 15-day daily cold (9 °C, 2.5 h) and heat (30 °C, 2.5 h) acclimation treatments on large, medium, and small Solenopsis invicta workers, followed by extreme temperature survival assays and comparative RNA-seq transcriptome profiling to uncover size-dependent acclimation phenotypes and molecular regulatory pathways. Survival results revealed that both cold and heat acclimation significantly boosted extreme thermal resistance of medium and small workers, whereas large workers exhibited inherently low mortality under lethal temperatures with no significant acclimation-induced survival improvement. Transcriptomic analyses showed striking body-size-specific transcriptional reprogramming: medium workers produced the largest number of differentially expressed genes (DEGs) under both acclimation regimes, followed by large workers, while small workers displayed minimal transcriptional shifts. Functional enrichment highlighted core pathways including lipid and small-molecule cryoprotectant metabolism, cuticle/membrane homeostasis, ion transport, antioxidant detoxification and sensory nervous signaling. Notably, hundreds of odorant receptor genes were sharply downregulated in acclimated medium workers, suggesting potential repression of olfactory function. Unlike acute thermal stress, long-term repeated acclimation triggered only mild transcriptional fluctuations of heat shock proteins with limited fold changes. Our findings demonstrate that thermal acclimation capacity in red fire ant workers is strongly correlated with body size, and coordinated remodeling of metabolic, osmotic, and chemosensory gene networks underpins this thermal plasticity. This body-size-dependent acclimation mechanism advances our understanding of invasive ant climate adaptation and helps predict their range expansion risks under global warming.

Moth auditory systems, evolutionarily adapted and structurally diverse with ultrasonic sensitivity, underpin the development of acoustic-based pest management strategies. Here, based on hypotheses derived from previous findings, we tested whether and how audible sounds (music, bird chirp, noise; 0.25–1 kHz, 80/120 dB) affect the development, survival, behavior and fecundity, as well as the molecular responses, using both short-term and long-term exposure (three successive generations) experimental designs. Behavioral assays showed dose-specific responses: high-intensity (120 dB) bird chirp and noise suppressed larval and adult activity, while low-intensity (80 dB) counterparts promoted larval crawling. Long-term exposure revealed that bird chirp and noise significantly impaired fitness, reducing larval/pupal body weight, pupation/eclosion rates, and egg hatching rate, with 120 dB noise exerting the strongest effects; 80 dB music showed neutral or positive impacts. Transcriptomic analysis identified 71–235 differentially expressed genes (DEGs) across treatment groups, with bird chirp and noise inducing more downregulated DEGs related to metabolism, immunity, and development. Notably, all cuticle-related DEGs in the 80 dB noise group and 53.2% in the 120 dB noise group were upregulated, suggesting stress-induced cuticular remodeling. GO/KEGG enrichment indicated distinct patterns: 80 dB music, bird chirp and 120 dB noise groups only had downregulated DEGs enriched in certain terms/pathways, mainly associated with cellular components; the 80 dB noise group had upregulated DEGs enriched in sensory, cuticle, metabolism and longevity-related terms/pathways, and downregulated DEGs in metabolism and human disease-related terms/pathways. Analysis of the expression patterns of all the longevity pathway-related genes suggested that sound stress induces lifespan regulation in this insect. These findings clarify S. frugiperda’s multidimensional responses to audible sound, providing a foundation for sound-based pest management.