Agonistic interactions between nymphs of Lycorma delicatula (Hemiptera: Fulgoridae)

The nymphs of Lycorma delicatula typically aggregate on tree branches for feeding. We studied agonistic interactions between nymphs in the field and investigated the effects of prior residence and body size on contest outcome. Resident nymphs maintained positions on tree branches and engaged in feeding, whereas intruding nymphs moved along tree branches. When an intruder approached, the resident typically raised its front legs as a threat posture. The intruder would either move away or palpate the resident, and the resident often lowered its body when palpated. The intruder would then attempt to shake the resident back and forth, with the number of attempts varying from one to several. The resident either maintained its position or fled. After a contest, the winner was determined to be the one occupying the contested position on the branch. The resident nymphs won 84.2% of the agonistic encounters, and the nymphs with larger body size won 63.2% of the agonistic encounters. Logistic regression analysis revealed that prior residence was a significant factor for the contest outcome, but body size was not. We discuss the hypotheses for the dominance of the residents in agonistic interactions between nymphs of L. delicatula. The nymphs of L. delicatula aggregate on branches of the tree of heaven ( Ailanthus altissima), sometimes in huge numbers. They feed on juices of the host plant by inserting stylets into the stems. These resident nymphs frequently encounter other nymphs who are passing along the tree branches. Such an encounter often results in an agonistic interaction between the resident and the intruder. After an agonistic interaction, the victorious individual stays on the feeding site, and the defeated individual leaves. The figures show the sequence of the agonistic interaction between the resident and the intruder in the nymphs of L. delicatula. (A) A resident (above) displays threat posture to an intruder (below). (B) The intruder (above) palpates its opponent (below). (C) The intruder mounts on the resident on the bottom of the branch. (D) The resident lowers its body. (E) The intruder shakes the resident with his front legs. (F) The resident (above) has successfully defended its position, and the intruder departs. [Display omitted]