The phenology and pollen feeding of three hover fly (Diptera: Syrphidae) species in Canterbury, New Zealand

The phenology and sex ratios of three hover fly species on Canterbury farmland, New Zealand were recorded weekly from five yellow watertraps from October 15, 1993 to January 31,1997. Gut fullness, egg number and pollen content were recorded weekly from September 8, 1994 to July 25, 1996. Catches of Melanostoma fasciatum (Macquart) and Melang\ma novaezelandiae (Macquart) were higher during the summer months, with maximum male M. fasciatum catches at 0.7 per trap/day in January, 1997. Catches of female Eristalis tenax Z97035 Received 15 October 1997, accepted 8 September 1998 L. peaked at 0.24 in August, 1994. Gut fullness and egg number in M. novaezelandiae and M. fasciatum were low from June to September, 1995, a pattern opposite to that of E. tenax. For all species combined, gut fullness was significantly higher in gravid females compared with non-gravid females, and males. Thirty-nine different pollen types were recorded from all hover fly classes. Male E. tenax (the largest of the three species) consumed the widest range of pollen in summer and autumn whereas females consumed the widest range in winter and spring, a pattern opposite to that of M. novaezelandiae. The value of the work in possible population enhancement programmes for hover flies in crops is discussed.