EUCALYPTUS NECTAR - PRODUCTION, AVAILABILITY, COMPOSITION AND OSMOTICCONSEQUENCES FOR THE LARVA OF THE EUCALYPT NECTAR FLY, DROSOPHILA-FLAVOHIRTA

In spite of the value of Eucalyptus species as honey plants, little is known about their nectar. This study examines patterns of nectar secr etion in E. ficifolia, the red-flowering gum, and E. cladocalyx, the s ugar gum. In both species evaporation was a major cause of diurnal var iability in nectar volumes and concentrations. Flowers of E. ficifolia secreted nectar throughout the day, but the greatest volumes were ava ilable in the early morning, in 2-3-day-old flowers, and when relative humidity was high. Larvae of the eucalypt nectar fly, Drosophila flav ohirta, which compete with honey-bees for this nectar, were much more abundant in Eucalyptus flowers than previously reported from the weste rn Cape. Measurements of nectar osmolality showed that Eucalyptus flow er cups are an osmotically stressful habitat for these larvae.