Figure 7.

Buzz ratio, defined as the fundamental frequency of floral sonication vibration divided by the fundamental frequency of flight vibration, for bees in the families Apidae and Halictidae, visiting flowers of Solanum elaeagnifolium, Pedicularis groenlandica, P. parryi, or S. dulcamara. Each data point corresponds to the buzz ratio for a single bee. Buzz ratio for bees visiting S. elaeagnifolium is shown in panels a and d, for P. groenlandica and P. parryi in panels b and e, and for S. dulcamara in panels c and f. Panels a–c show the relationship between buzz ratio and bee size (ITD, mm). Panels d–f show boxplots of the same data grouped by bee species. Bee species are arranged from smallest to largest. Panel g shows the buzz ratio across all bees in Apidae and Halictidae for each of the plant species studied. The dashed line corresponds to a buzz ratio of 2.0, that is, floral vibration frequency is double the flight vibration frequency