Diurnal Foraging Behavior of an Aphidophagous Hoverfly in an Insectary Plant Patch

Abstract

A series of foraging bouts of Episyrphus balteatus (DeGeer) females were observed and recorded throughout the day in phacelia (Phacelia tanacetifolia Bentham) patches. The dominant transitions of interplant movement, approaching and probing bouts were statistically more frequent in the morning than in the afternoon. In the morning, interplant movement of foragers was significantly longer and they were moving at higher places of phacelia patches. They approached and probed flowers considerably longer in morning compared to afternoon. A significant positive relationship between the number of open flowers in a patch and the patch residence time was observed in the morning. The proportion of females having swollen abdomen filled with phacelia pollen (68.2%) in the afternoon was significantly higher than that (31.82%)in the morning. In our study, E. balteatus females spent more time foraging in phacelia patches in morning compared to afternoon. Based on the results and by considering the dual resources requirements of a female hoverfly (flower foraging and searching for aphids to lay eggs), we will discuss the effective diurnal foraging of E. balteatus females in phacelia patches.