Evidence of orchid visitation by Bactrocera species (Diptera: Tephritidae) in Papua New Guinea.
The orchid-fruit fly (Bactrocera spp.) interaction in Papua New Guinea was investigated using pollinaria as a marker of orchid visitation. Fruit flies were collected from June 1998 to September 1999 from all provinces in Papua New Guinea (PNG), except Western, Gulf and Southern Highlands, using cue-lure/raspberry ketone and methyl eugenol (ME) traps. A total of 338 pollinaria- bearing flies belonging to 24 Bactrocera spp. were recorded. Sixteen of the 20 most frequently trapped species with pollinaria-bearing individuals belonged to the subgenus Bactrocera, although species from other genera (i.e. Dacus) or subgenera were also recorded. Pollinaria-bearing flies were not collected from the Papua New Guinea Highlands (covered by Western Highlands, Chimbu and Eastern Highland Provinces), while a large number of these flies were caught in the Morobe Province (83% of pollinaria-bearing flies, 40% of total flies sampled from pollinaria-bearing species). The location of pollinaria on a fly's body depended on whether the fly was a ME- or a cue-lure-responding species. For most of the ME species, pollinaria were always located on the mesothorax. For most of the cue-lure flies (77%), pollinaria were placed on the terga II-IV of the abdomen. B. trivialis was unusual among the cue-lure flies in that all individuals carried pollinaria on the thorax. For B. curvifera, B. musae and B. umbrosa from Morobe Province, the monthly total of pollinaria-bearing flies was significantly correlated to the total monthly catches of these species in the province. This suggests that the collection of flies with pollinaria was related to the total population size rather than being influenced by factors specific to fly-orchid interaction (e.g orchid flowering times).