Phenology and ecology of hoverflies (Diptera: Syrphidae) in New Zealand.
Syrphids are potentially important in many agricultural and horticultural crops as biological control agents. The two most abundant species present in the New Zealand agricultural landscape are Melanostoma fasciatum and Melangyna novaezelandiae, both of which are aphidophagous and also prey on young lepidopteran larvae. Information regarding the phenology and ecology of these species is quite limited but is needed if the contribution of these predators to biocontrol is to be enhanced. The main work reported here concerns the trapping of large numbers of syrphids to investigate their phenology; these flies were subsequently assessed for the pollen type taken and for wing wear. Foraging behaviour, optimal trap colour, and ideal trap-emptying rate were also studied. There was good evidence of a second generation of syrphids occurring in late summer and pollen preferences for both species were exhibited. The foraging behaviour of the two species differed in relation to the number of flights made and the overall distance travelled over fixed time intervals. Yellow was the most efficient colour for trapping M. novaezelandiae but for Melanostoma fasciatum yellow, white and blue did not differ and green was poor. The value of the work in providing background ecological information for possible enhancement programs for hoverfly populations on farmland is discussed.