Abstract
1. The breeding season of H. ustulata extends over a 2 1/2 month period in the Sonoran desert near Phoenix, AZ. Individual males are active on mountain ridges for periods averaging about 3 weeks for those wasps captured in the first half of the flight season. Many males live more than 1 month. 2. Some palo verde trees chosen as landmark territories by male wasps are occupied earlier in the flight season and more consistently thereafter than others. Preferred territories tend to be located higher on ascending ridges. 3. There is considerable turnover in territory ownership at some trees during the course of the flight season. The average duration of residence by a male wasp was 8 days for all occupants of 18 trees followed over the breeding period. Some changes in ownership occur because an intruder defeats the resident in an aerial contest. Small males are replaced by large ones at preferred territories over the course of the flight season. 4. Smaller males can adjust their behavior to their social evironment, claiming low-ranking territories if excluded from favored trees or holding prime territories during days when large males are absent. Alternatively, they may abandon territoriality altogether to patrol a series of trees along a ridge. 5. Despite an abundance of males (>350 marked), females were rarely seen and only two copulations were observed. Male territoriality was not focused directly on emerging or nesting females nor was it focused on food resources attractive to females. The breeding season was prolonged (2 1/2 months) and the operational sex ratio heavily skewed toward males. The wasp's mating system resembles lek polygyny in the sense of Emlen and Oring (1977).
Published Version
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