Foraging Behavior of an Aphidophagous Hoverfly, <I>Sphaerophoria macrogaster</I> (Thomson) on Insectary Plants.

BACKGROUND AND OBJECTIVE: Flower resources are prerequisites for survival and reproduction of aphidophagous hoverflies adults. It is, therefore, necessary to evaluate their foraging behavior with regards to different flowering species in order to utilize hoverflies to enhance conservation biological control (CBC) of aphids.

MATERIALS AND METHODS: The foraging behavior of the female hoverfly, Sphaerophoria macrogaster (Thomson) was observed in coriander (Coriandrum sativum Linnaeus) and blue salvia (Salvia farinacea Bentham) flower patches using a focal sampling method combined with continuous recording. The sequences and durations of all foraging bouts were recorded during the residence of observed S. macrogaster in each flower patch.

RESULTS: Significantly more transitions from searching to assessment of flowers were noted in coriander than in blue salvia flower patches (χ2 = 4.55, p<0.05). However, approaching to probing transitions were significantly more frequent in blue salvia than in coriander flower patches (χ2 = 9.59, p<0.05). Foragers showed significantly prolonged inter plant movement but shorter probing durations in coriander flower patches. Of interest, total duration of time spent in patches by S. macrogaster did not differ significantly between coriander and blue salvia.

CONCLUSION: Results from the present study illustrated that both flowering plant species were apparently attractive to Sphaerophoria macrogaster females but these foragers preferred coriander flowers. This finding may form the basis of flower selection in and around the crop fields for enhancement of this aphidophagous natural enemy to maximize the biological control of aphids.