Effect of flower density on foraging of Lycaena dorcas

Abstract

The purpose of this study was to examine if individual Lycaena dorcas were flower constant and to determine if floral density and display had an affect on L. dorcas foraging. Data was collected at a beach near Waugoshance Point in Northern Lower Michigan. Several L. dorcas individuals were followed to determine their preferred flower, and then plots were made that contained low density and high density of the preferred flower along with some mixed plots of the preferred flower and one other species. L. dorcas was found to only visit Potentilla fruticosa flowers, thus constancy of individuals could not be tested. We found that plot density has a significant positive effect on number of butterfly visitors to the plot; we found marginally significant positive effects of density on total time spent by butterflies in the plot and the visitation rate. Overall, more butterflies were found in high density plots of P. fruticosa and L. dorcas spent more time in higher density plots than in low density plots; mixed plots were visited the least. These results are consistent with optimal foraging theory because the butterflies visited plots that had high densities of their preferred flower much more and spent more time in high density plots, minimizing their searching efforts for the greatest net energy intake.