Wataru Kojima, a lecturer at Yamaguchi University, discovered that beetles occupying sawtooth oak sap fields at night are thrown down by giant hornets early in the morning and take over the feeding grounds within minutes.
Many insects gather in the sawtooth sap field, but their appearance is completely different between day and night.During the daytime, they are mainly butterflies, bees, and canaries.Among them, the giant hornet stands at the top of the hierarchy, driving out other species of insects and monopolizing the sap field.At night, beetles, moths, stag beetles, etc.Among them, the exceptionally large beetle is the most dominant species.What would happen if a giant hornet and a beetle met?
Therefore, we observed the beetles that gather in the sap field in the sawtooth oak forest in Yamaguchi Prefecture.Around 5:10 in the morning, several giant hornets that came to the sap field bit the legs of the beetles and threw more than 3 of them down one after another.The sap fields were hijacked in minutes.Beetles may also attack after falling to the ground.Such exclusion behavior was observed early in the morning on all three days.
And when wasp sprays continued to keep giant hornets out of the sap fields, more than half of the beetles remained in the sap fields until at least noon.This means that beetles are not naturally very nocturnal and can be active during the day if they are not attacked.In fact, in ash trees, where there are many feeding grounds per tree, wasps rarely attack the beetles, allowing the beetles to stay and feed during the day.
Our observations indicate that the active time of beetles is changed by attacks from Asian giant hornets.The beetles may be "forced" to be nocturnal, he said.
Paper information:【Ecology】Temporal niche shifts driven by interference competition: Giant hornets excluderhinoceros beetles at sap sites at dawn
