DISPERSAL AND EFFECTS OF BARRIERS ON THE MOVEMENT OF THE NEW-ZEALAND HOVER FLY MELANOSTOMA-FASCIATUM (DIPT., SYRPHIDAE) ON CULTIVATED LAND

Dispersal within agricultural fields and the effects of different barr iers on between-field movement of the New Zealand hover fly Melanostom a fasciatum were studied using ingested pollen as markers. Hover flies did not generally disperse more than 20 m from the pollen source. Gra vid females had no significant wind-directed movement pattern whereas males significantly flew downwind. Flies tended to avoid flying over b arren land: a dirt track, an asphalt road or a ploughed field all seem ed to hamper hover fly dispersal equally. The implications for spatial arrangement of the flowering strips to enhance the biocontrol potenti al of hover flies are discussed.