Host preferences of aphidophagous hoverflies from field distribution of their larvae

The patterns of occurrences among aphid colonies of the larvae of two species of highly polyphagous predatory hoverflies, Episyrphus balteatus (de Geer) and Syrphus ribesii (L.) (Diptera: Syrphidae), were assessed in three areas (Nottingham, Cardiff (UK) and the Czech Republic); in the last two sites, larvae of other syrphid species were also identified. The two syrphid species showed considerable diet overlap, their larvae using many of the same aphids as food, but with significant exceptions. Together with information from the literature, even for these very generalist species there was a consistent pattern of preference among aphid species. Most other species showed restricted preferences. Larvae were more frequent on developed aphid colonies than on colonies that were younger or had almost disappeared.