The mating system of a bee fly (Diptera: Bombyliidae). I. Non-resource-based hilltop territoriality and a resource-based alternative

The mating system of an undescribed Australian bee fly (Comptosiasp. near lateralisNewman) was studied in Southeast Queensland. Males perched in clearings on a wooded hilltop and darted toward nearby flying insects. On sunny days males interacted with other insects about once per minute. A minority of these interactions was with conspecific males. They had the effect of determining ownership of the perching area. Most conspecific interactions occurred withtin 90 min of the first male's arrival each day, although territories were occupied for an average of 4.6 h per day. The same territories were used by different generations of flies for at least 4 years, while other apparently similar clearings on the hilltop remained unoccupied. Following removal of resident males, replacement males occupied the sites in 12.5 min on average. Females were not observed on the hilltop except when mating at territories. No interactive courtship behavior was detectable prior to midair coupling. Copulations lasted for 118 min on average. We interpret this as a landmark-based mating system and discuss it in relation to the concept of lek polygyny. Observations of Comptosiasp. near lateralismatings at a nonhilltop, resource-based encounter site suggest that the mating system of this species varies in response to the distribution of resources.