Aggressive interactions often occur between individuals of various insect species attracted to fermented tree sap. We explored interspecific behavioral dominance hierarchies and factors responsible for such interactions occurring in sap-exuding patches on trees. We observed fighting behavior, departures from patches, and attempted entries into patches (individual approached and then left a patch without feeding) in four hornet species (Vespidae), four butterfly species (Nymphalidae), and one beetle species (Scarabaeidae). Our examination of these interactions indicated that the hornet species, Vespa mandarinia Smith, was the most dominant and that butterfly species were competitively inferior. Both Vespa ducalis Smith and Rhomborrhina japonica Hope were less dominant than Vespa crabro L. and Vespa analis F. in departures and attempted entries into patches, but neutral when it came to fighting behaviors. For most hornet and butterfly species, approach and threat behaviors were mainly responsible for departures and attempted entries, respectively, indicating that individuals of these species avoid fights by recognizing the behaviors of other individuals. These results suggest that competitor-avoidance behaviors play an important role in foraging success at sap sites, highlighting the importance of examining these behaviors as well as aggressions before determining dominance hierarchies. Competitor-avoidance behaviors of subordinate species might enable them to forage in patches and potentially affect the co-occurrence of sap-attracted insects.