Great Basin Naturalist


Nectar-sugar concentrations and major flower visitors were determined for 15 species of plants in the Eagle Lake area of Northeastern California. Sugar concentrations for 12 of these are reported for the first time, with means ranging from a low of 10 percent in Mentzelia laevicaulis to a high of 63 percent in Ranunculus uncinatus. The utilization of the various nectar concentrations varied with the type of flower visitor as well as with the habitat and distributional ranges of the plant and/or animal. Hummingbirds and hawkmoths were not observed visiting the flowers they typically visit in other areas (e.g. Aquilegia and Ipomopsis, or Oenothera), but here preferred more concentrated nectar (Cirsium spp., with mean of 57 percent sugar). Specialization in nectar use is reported at the generic and specific level in Hymenoptera and Lepidoptera; solitary bees, as a whole, used slightly less concentrated nectar (x̄ = 38 percent sugar) than butterflies (x̄ = 44 percent sugar).