Ant‐Homoptera Interactions in a Neotropical Savanna: The Honeydew‐Producing Treehopper,Guayaquila xiphias(Membracidae), and its Associated Ant Fauna onDidymopanax vinosum(Araliaceae)1

We investigate the ant fauna associated with the Neotropical treehopper,Guayaquila xiphias, on shrubs ofDidymopanax vinosumin the cerrado (savanna) of SE Brazil. Treehoppers infested plants at the border of the cerrado almost exclusively and preferably fed near the apical meristem. During the reproductive phase of the host plant, however, the vast majority of the treehoppers aggregated on the inflorescences. We found 21 ant species harvesting honeydew atG. xiphiasaggregations, the most frequent beingCamponotus rufipes, Ectatomma edentatum, C. crassus, andC. renggeri.Such a taxonomic diversity of ants tendingG. xiphiasaggregations in the cerrado is far greater than that reported for any other ant‐homopteran system. Daily turnover of ant species at a given treehopper aggregation was observed on 29 percent (64 out of 222) of theG. xiphiasaggregations recorded onD. vinosumshrubs. Species replacements probably reflect distinct humidity and temperature ranges tolerated by the species, and may ultimately reduce interspecific competition at homopteran aggregations. Since predation and parasitism onG. xiphiascan be severe, and tending ants protect the homopterans against predators and parasitoids, the round‐the‐clock activity by ants atG. xiphiasaggregations is regarded as crucial for the survival of these treehoppers in the cerrado.