A long-term study of male territoriality in the tarantula hawk wasp (Hemipepsis ustulata; Pompilidae) in Central Arizona

Abstract Males of the tarantula hawk wasp Hemipepsis ustulata defend individual trees and shrubs growing on ridges and peaks in the Sonoran Desert of Arizona. Territories occupied by males of this wasp species have been monitored in the Usery Mountains of central Arizona for nearly 4 decades. Although previous research indicated that males abandoned their territories by midday, in this study some territories continued to be occupied until as late as 1600h Mountain Standard Time (MST). Territories held into the afternoon included those that were taken early and late in the flight season and which were most-frequently occupied overall. Individual plants that were most likely to attract territorial males during five previous studies were also the most popular territories in 2016. Likewise, many other features of the territoriality of male tarantula hawks have usually been similar during most of the five previous studies of the wasps, including the tendency of larger males to occupy highly ranked territories as residents, the total number of sites occupied by resident males, the mean duration of residency, the total number of male territorial residents during the flight season, and the maximum number of occupied territories on any given day. Results from 2016 provided confirmation that the standard pattern is robust with one partial exception, 1998, a spring in which for unknown reasons the number of tarantula hawk wasps was unusually large and the number of occupied territories was correspondingly large.