Ecology of Northern Australian Dacinae (Diptera: Tephritidae) II*. Seasonla Fluctuations in Trap Catches of Dacus opiliae and D. tenuifascia, and their Relationship to Host Phenology and Climatic Factors

Abstract

Changes in trap catches of male Dacus opiliae Drew & Hardy were studied in northern Australia by use of permanently maintained groups of Steiner traps baited with methyl eugenol, an attractant for males of this species. D. opiliae, which is monophagous on a wet-season host species, was common in traps from October to February (wet season) and rare for the remamder of the year. In a second species, D. tenuifascia (May), which is monophagous on a dry-season host, trap catches peaked during the period from August to October after commencement of host fruit production. D. tenuifascia was not absent from traps at any time of the year. Temporal aspects of the seasonal fluctuations of trap catches of D. opiliae could not be explained solely on the basis of increases due to reproduction. Other features, such as the disappearance of D. opiliae from mainland traps during the dry season, were also difficult to explain. It is concluded that changing dispersive behaviour and variable lure response of males. both controlled by environmental variables, may have strongly influenced the observed fluctuations.