Environmental influences on hovering behavior of Tabanus nigrovittatus and T. conterminus (Diptera: Tabanidae)

Hovering aggregations of males of T. nigrovittatus and the sibling species T. conterminus were observed on salt marshes in southern New Jersey. Males of T. nigrovittatus hovered over expanses of short marsh grasses, while T. conterminus hovered over tidal creeks and near other prominent landmarks. T. nigrovitattus exhibited 2 distinct daily hovering periods. The timing of these periods varied daily but showed a strong negative correlation with ambient temperature. A principal-components analysis identified a combination of ambient temperature, black-body temperature and light intensity as most predictive of hovering onset. T. conterminus hovered during a time period which was generally intermediate to the 2 hovering periods of T. nigrovitattus. Temporal partitioning of hovering "windows" may represent a premating isolating mechanism.