Hover flies (Diptera: Syrphidae): Trap efficiency, phenology and pollen feeding : A dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Horticultural Science with Honours

Abstract

Hoverflies show potential as biological control agents of aphid populations; however, additional information is required on the ecology and phenology of New Zealand hoverflies to minimise their contribution to biological control. The adult flies use nectar for energy and pollen for egg maturation, so an increase in floral diversity may enhance hoverfly numbers and, in turn, aphid predation. The phenology of the two aphidophagous hover fly species, Melanostoma fasciatum (Macquart) and Melangyna novaezelandiae (Macquart) as well as that of the nonaphidophagous species Eristalis tenax L. were monitored over a two year period. The primary objective was to determine whether higher amounts of pollen in the immediate environment increased the number of hover flies, the proportion of gravid females and the proportion of hoverflies with guts with high amounts of pollen. A secondary objective was to investigate the effect of trap colour (yellow-sided traps versus green-sided traps) on the populations of hover flies caught.