The nymphs of the lantern fly, Lycorma delicatula, typically aggregate on tree branches for feeding. We studied the agonistic interactions between nymphs in the field and investigated the effects of residence and size asymmetries on contest outcome. Resident nymphs took positions and engaged in feeding on tree branches, whereas intruding nymphs moved along tree branches. When intruders approached, residents typically raised their front legs as a threat sign. Intruders would decide to either move away or palpate residents, and residents often lowered their position when palpated. Then, intruders would attempt to shake residents back and forth, and the number of attempts varied from once to several. Residents either maintained its position or fled away. After a contest, the winner was determined as the one which occupied the position it fought over. Resident nymphs won 84.2 % of the agonistic encounters, and nymphs with bigger body size won 63.2 % of the agonistic encounters. The result of the logistic regression analysis revealed that residence was a significant factor for contest outcome, but body size was not

The nymphs of the lantern fly, Lycorma delicatula, typically aggregate on tree branches for feeding. We investigated effects of residence and size asymmetries on the agonistic interactions between nymphs in the field. Resident nymphs took positions and engaged in feeding on tree branches, whereas intruding nymphs moved along tree branches. When intruders approached, residents typically raised their front legs as a threat sign. Intruders would decide to either move away or palpate residents, and residents often lowered their position when palpated. Then, intruders would attempt to shake residents back and forth, and the number of attempts varied from once to several. Residents either maintained its position or fled away. After a contest, the winner was determined as the one which occupied the position it fought over. Resident nymphs had a winning rate of 84.61% in agonistic encounters, and the winning rate increased to 87.5% when residents had bigger body sizes than intruders. Bigger individuals had won 61.54 % of agonistic encounters. The behavioral analyses of the agonistic encounters suggested that asymmetry in residence had a strong effect on the outcomes of agonistic encounters, with asymmetries in body sizes producing a weaker effect.