Floral Nectar

Müller (1883) and Faegri and van der Pijl (1966) present several ways that flowers attract pollinating insects: appeal to the sexual nature of the insects, offer a favorable microclimate or shelter, attract them with the visual (either color or movement) and chemical (odor) aspects of the flower, or offer floral rewards. Obviously, nectar falls into the latter category. Although some flower species can produce thousands of microliters of nectar per nectary, most nectaries generally produce less than 10 μl (Opler, 1983; Pacini et al., 2003; Petanidou et al., 1996; Stiles and Freeman, 1993; Watt et al., 1974). In fact, some stingier plants have no nectar at all; one estimate is that nearly 14% of plants in Mediterranean phrygana are nectarless (Petanidou et al., 1999), but these plants may produce other rewards. A number of factors influence the interactions of floral nectar and insects, most notably when and where floral nectar is supplied and its nutrition and defense.