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. © 2025 Society of Chemical Industry.