Abai, MR

6th International Congress of DipterologyThe use of acute and marked wings in the courtshipbehavior of Hercostomus sp. (Dolichopodidae)Satô, M.Rishiri Town Museum, Senhoshi, Rishiri Is., Hokkaido 097-0311, JapanModifications or ornamentations of the wings have been described assecondary sexual characters of the males in numerous species ofDolichopodidae. They provide good characters for the identification ofspecies and may stimulate considerations about a correlation between thesemorphological characters and courtship behavior (Lunau, 1992; Zimmer etal., 2003).A new species of Hercostomus found by K. Masunaga and the author inSouthern Japan was observed on the surface of leaves or rocks on thebanks of rivers. The males have the most curious wings among the knownJapanese dolichopodid flies. The wings are acute and elongated toward thetip which bears a black and white spot on a small circular area. Although itshould be expected that wing modifications are restricted by therequirements of flight, the present modifications do not only affect theoutline of the wing surface and its coloration. The small circular tips aretwisted and crossing each other above the abdomen in the resting position.The coloured and twisted wing tips are very conspicuous when viewedfrom behind the fly, together with contrasting black bands on the yellowhind femora.Courtship was observed exclusively on leaves in the shade. The sequenceof the male’s behavior is usually performed in the following order; 1) flightdisplay, 2) position behind female, 3) wing-opening in vertical posture, 4)wing-fanning display in vertical posture, 5) wing-fanning display inhorizontal posture, 6) wing-fanning display at a slow speed in verticalposture and 7) try to copulation. The small circular tips are displayedbeside the potential mate's eyes in wing-fanning display in horizontalposture. This observation confirms that the wing modifications of thisspecies are actually used in its courtship behavior. Continued fieldobservations may help to assess the role of signal enhancement in the viewfrom behind.219