Foraging behaviour of Apis florea F., an important pollinator of Allium cepa L.

The foraging behaviour of insect visitors to onion (Allium cepa L.) flowers was studied in relation to five environmental variables. The dwarf honey bee Apis florea L. was the most abundant flower visitor, and comprised more than 94% of the total visitors. Commencement of flight activity occurred when a minimum threshold of environmental variables was exceeded, while the cessation was governed mainly by decline in light intensity and radiation. The foraging population correlated significantly and positively with air temperature, light intensity, solar radiation and nectar-sugar concentration and negatively with relative humidity. Path coefficient analysis, revealed, however, that the direct effect of temperature was large and positive followed by light intensity and solar radiation while the direct effect of relative humidity was small and negative. The direct effect of nectar-sugar concentration was positive and negligible. Path coefficient analysis thus gave a clearer picture of the effects than did a simple correlation analysis. On average A. florea visited 1.33 +/- 0.26 and 6.17 +/- 0.58 umbels and flowers/min, during different hours of the day. The insect pollinated plots produced significantly more seeds with heavier weights than those isolated from insect visits.