Spatial and Temporal Components of Resource Assessment by Flower-Feeding Insects

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Abstract
Per-flower insect visitation rates on 2 plant species within Rocky Mountain subalpine meadows were measured using fluorescent powders and found to be positively correlated with local flower density, suggesting that insects concentrate their foraging in dense patches of flowers. Visitation rates on both species are also correlated with the presence of other plant species which share the same visitors; these correlations are positive, suggesting cooperative rather than competitive plant-plant relationships, at least insofar as visitation is concerned. By correlating local visitation rates with flower densities computed over a range of block sizes, the block sizes at which insects assessed flower density differences were estimated to be approximately 1000 m2 for solitary bees and flies visiting Potentilla spp., and 500 m2 for bumblebees visiting composites. By correlating local visitation rates with flower censuses from various days before the visitation measurements, the time lags in flower density assessment were estimated to be approximately 1.5 days for the solitary bees and flies, and 0.5 days for the bumblebees. Implications for plant competition and flowering strategy are discussed.