Pollination by Monkey Beetles (Scarabaeidae: Hopliini): Do Color and Dark Centers of Flowers Influence Alighting Behavior?

Abstract

Monkey beetles (Scarabaeidae: Rutelinae: Hopliini) visit mostly unscented flowers with conspicuous dark center patterns that have been suggested to mimic resting beetles. Field observations in South Africa showed that monkey beetles are the primary pollen vectors of the dark-centered flowers of Ixia dubia Vent. (Iridaceae) and Spiloxene capensis (L.) Garside (Hypoxidaceae), and the dark-centered flowerheads of Gazania pectinata (Thunb.) Spreng. (Asteraceae). Monkey beetles used the flowers of these species as mating rendezvous sites and consequently showed a significant clumped distribution in flowers. We used model flowers approximating the study species to determine which traits are important for eliciting alighting behavior in monkey beetles. Contrary to expectations, beetles did not significantly prefer dark-centered to plain models in 7 of 8 independent experiments, nor did beetles discriminate significantly between plain models and models with male or female beetles glued to their surface. However, beetles did show a strong preference for orange over red, yellow, and blue models. The results of this study indicate that alighting behavior of monkey beetles is influenced primarily by flower color rather than flower patterning or presence of other beetles.