Biogenic amines modulate cannibalistic behaviors in the fall armyworm, Spodoptera frugiperda

BACKGROUND Cannibalism, defined as the ingestion of an individual by another individual from the same species, is a phenomenon prevalent across various animal groups, particularly among the larvae of the fall armyworm, Spodoptera frugiperda . These larvae exhibit cannibalistic tendencies under specific environmental conditions. RESULTS This study demonstrates that cannibalism is rarely observed during the first‐ and second‐instar stages in S. frugiperda . The highest proportion of cannibalism was recorded among fifth‐ and sixth‐instar larvae, with a clear increasing trend observed from the fourth‐ to fifth‐instar stages. Starvation and high‐density rearing conditions are some factors that significantly enhance the frequency of cannibalism. Among the biogenic amines tested, only octopamine and the expression of its rate‐limiting enzyme gene TβH were significantly elevated under starvation and crowded conditions. Furthermore, treatment with octopamine, a neuroactive compound, substantially increased the frequency of cannibalistic attacks in the fifth‐instar larvae. Conversely, supplementation with phentolamine, an octopamine receptor antagonist, effectively suppressed starvation‐induced cannibalism. CONCLUSION These findings indicate that octopamine is a critical mediator of cannibalistic behavior in S. frugiperda . This insight may offer a foundation for developing novel pest control strategies targeting behavioral modulation in S. frugiperda .