Fig. 7.

Experiments with two flowers of Ophrys heldreichii in Crete (Greece) to test whether males of Eucera berlandi are able to distinguish flowers of the same plant (test series I) and flowers of two different plants (test series II). Series I: two flowers presented open with both visual and olfactory signals accessible to the bees. Series II: flowers inside plexiglass boxes with a UV-permeable front side and barring the bees from flower olfactory stimuli. To attract the male bees, smell of Ophrys heldreichii flowers cumulated in a box beforehand was blown to the right and left sides of the front glasses. To prevent side preferences (because of the wind) each 10 min. flower position was exchanged. Whereas in test series I male bees could land on the flowers, in test series II strong attempts to land by tipping at the front glass were counted as attempts to pseudocopulate (ps) and short tips as trials to land (sl). Approaches to the flowers without landing were counted as well (ap). Flowers of the same plant individual and presented open are distinguished only weakly and caged flowers, with the visual cues only, not at all. In contrast, flowers of different plants are well distinguished in both situations. Obviously, male bees are able to select between different plant specimens. Cumulation of several test series in different years. Ps, pseudocopulations; sl, short landings; ap, approaching without landings

(modified from Paulus 2007)