Estimating attraction of Syrphidae (Diptera) to flowering plants with interception traps

Abstract

Syrphidae with predaceous larvae are important predators of aphids and other insects and can be attracted and maintained in agricultural environments by the addition of flowering plants. Malaise interception traps baited with moveable flowering plants are a novel means of surveying for attractive species and can have the advantages of: (1) homogenising experimental site and plant quality, (2) portability, (3) continuous sampling, (4) capacity to simultaneously capture a broad range of insects (including pests) and (5) no requirement for additional sensory cues to be effective. Six of the 10 species of plants tested were relatively attractive (number of syrphids captured in flower-traps/numbers captured in no plant controls). While flower-traps captured more syrphid species than their associated controls, there were no differences between flower-traps and controls in the sizes (head height) or proboscis lengths of the flies collected. There were no significant relationships between relative attractiveness and flower width or depth or with plant height and floral area. Similarly, mean proboscis length of flies taken in flower-baited traps was not correlated with flower width or depth. The absence of the latter relationship may be due to the inability of an interception trap to distinguish between attraction and attraction-then-feeding.