Two-way predation between larvae of Spodoptera frugiperda and Spodoptera litura

Spodoptera frugiperda has co-occurred with Spodoptera litura in corn fields since it invaded China on December 2018. In our process of rearing S. frugiperda and S. litura larvae in the lab, we discovered that when the larvae of S. litura and S. frugiperda were on the same host plant, two-way predation between them occurred. However, a detailed study on this phenomenon has not been previously reported. Therefore, the study on the two-way predation between larvae of S. frugiperda and S. litura was performed under mimicking natural conditions including the presence or absence of maize leaves. The results showed that 4th instar larvae of S. frugiperda could prey actively on the 3rd instar larvae of S. litura under natural conditions in the greenhouse, and there was two-way predation between S. frugiperda and S. litura larvae in either the presence or absence of maize leaves in the lab. In addition, the difference in the daily predation number of old S. frugiperda larvae (including 4th,5th and 6th instar) on S. litura 1st, 2nd and 3rd instar larvae respectively was significant between presence and absence of maize leaves. Similarly, the difference in the daily predation number of S. litura old larvae (including 4th, 5th and 6th instar) on S. frugiperda young 1st, 2nd and 3rd instar larvae respectively was very significant between presence and absence of maize leaves. These results confirm that two-way predation exists between larvae of S. frugiperda and S. litura, and S.frugiperda larvae are in a dominant position in this struggle, which provides an understanding of S. frugiperda feeding when coexisting with S. litura.