Geomagnetic intensity variation and deprivation elicit distinct transcriptomic responses in a migratory insect

Geomagnetic field intensity varies along migratory routes; however, whether migratory insects respond similarly to intensity shifts and geomagnetic deprivation remains unclear. We compared transcriptomes of brown planthoppers, Nilaparvata lugens (Stål), reared under ~45 μT or ~50 μT fields, approximating intensities along their migratory route, or under a near‐zero magnetic field (NZMF). The natural‐range ~5 μT comparison identified 244 DEGs and a restricted functional response. ‘Lipid transporter activity’ was the only Gene Ontology term significant after false‐discovery‐rate correction, whereas ‘response to light stimulus’ and ‘flavin adenine dinucleotide binding’, both containing cryptochrome1 ( Cry1 ), were nominally enriched. By contrast, NZMF identified 2753–3258 DEGs and enrichment of central carbon and amino‐acid metabolism, peroxisomal function, redox regulation and clock‐related genes. RT‐qPCR validated representative genes. Given its differential expression under ecologically relevant geomagnetic intensity variation, established photoreceptive and circadian functions and previous NZMF responsiveness, Cry1 was examined by RNA interference as a step toward an eclosion‐based magnetic response assay. Cry1 knockdown disrupted the diel eclosion rhythm, demonstrating its importance for eclosion timing and limiting this phenotype as a magnetic field intensity readout after knockdown. Together, natural‐range geomagnetic variation and NZMF exposure may evoke qualitatively distinct magnetobiological response states rather than quantitatively different magnetic environments.