Visual detection of diminutive floral guides in the bumblebee Bombus terrestris and in the honeybee Apis mellifera

Abstract

Many flowers display colour patterns comprising a large peripheral colour area that serves to attract flower visitors from some distance, and a small central, contrastingly coloured area made up by stamens or floral guides. In this study, we scaled down the size of floral guides to detect the minimal size bumblebees (Bombus terrestris) and honeybees (Apis mellifera) require for guidance. We analyzed the approach and the precise contact of the antennal tips with the floral guide of artificial flowers which precedes landing and inspection. Both bumblebees and honeybees were able to make antennal contact with circular floral guides which were 2 mm in diameter; bumblebees performed better than honeybees and antennated also at floral guides smaller than 2 mm. In discrimination experiments with bumblebees, a minimum floral guide size of 2 mm was required for discrimination between artificial flowers with and without floral guides. With increasing experience bumblebees targeted close to the site of reward instead of making antennal contact with the floral guide, whereas honeybees did not alter their initial behaviour with growing experience. Bumblebees and honeybees spontaneously target diminutive floral guides to achieve physical contact with flowers by means of their antennae which helps them to inspect flowers.

The innate responses of bumble bees to flower patterns: separating the nectar guide from the nectary changes bee movements and search time

“…1). Both visual elements are visible to bumble bees, which can discriminate a floral nectar guide that is ≥0.5 mm in diameter at close distances, such as when they walk on the flower (Lunau et al 2009). On the disjunct feeders, the nectary was displaced 37 mm away, to the opposite side of the feeder (Fig.…”

“…Bumble bees can approach and discriminate artificial flowers with circular nectar guides at least 2 mm in diameter over artificial flowers without nectar guides (Lunau et al 2009). However, as they approach a flower, bumble bees can detect even smaller nectar guides and will antennate artificial flowers with circular nectar guides as small as 0.5 mm (Lunau et al 2009). Leonard et al (2013) used a white artificial flower with a central dark nectary that was 2.5 mm in diameter.…”

The influence of pigmentation patterning on bumblebee foraging from flowers of Antirrhinum majus

“…This particular form of nectar guide has long been known to increase floral attractiveness to a range of pollinators. Bumblebees and honeybees have been shown to discriminate bull's eye spots as little as 2mm in diameter (Lunau et al 2009). In a series of classic experiments with Delphinium nelsonii, which has a white centre in a deep blue flower, Waser and Price (1983;1985) showed that the central colour patch improves foraging efficiency of both bees and hummingbirds by reducing time to find the flower and time to access the reward.…”

Getting to the start line: how bumblebees and honeybees are visually guided towards their first floral contact

“…2 cm; Goulson et al, 2007); entering a corridor, in which a pattern is contained, in a maze (Simonds and Plowright, 2004;Séguin and Plowright, 2008); antennal contact with a test pattern (Pohl et al, 2008;Lunau et al, 2009)-see Fig. 1 for an illustration with honeybees and bumblebees; landing on a test pattern (Leonard and Papaj, 2011); floral exploration as defined by walking into an artificial flower (Orbán and Plowright, 2013); or probing (Daumer, 1958).…”

“…Flowers with a dot or pair of dots at the centre of flower (Fig. 1) are more likely to be approached and antennated by flower-naïve bumblebees (Heuschen et al, 2005), with bigger dots eliciting stronger responses by both honeybees and bumblebees (Lunau et al, 2009). …”