Wild bees are specialists

Nectar and pollen are the bees' most important food source: nectar, which is rich in sugar, provides energy, while pollen provides proteins, fats and vitamins that are essential for rearing brood.
Red bryony and white bryony grow wild in hedgerows and along fences. The wildbee Andrena floreaThe fence beet sand bee only collects pollen from these two climbing plants.Their nectar serves as food for the adult bees - as is often the case in such cases. At flowering time, several males often patrol the forage plant: they are looking for female mating partners.
Andrena florea builds its nest in sandy,  sparsely vegetated soil near its food plants. The red marked abdomen and the close relationship to bryonies are characteristic for this wild bee species.

Image captions:
Male flower of Red Bryony  (Bryonia dioica JACQ.)
Andrena hattorfiana collects pollen only on Scabiosa and Knautia species (middle). 
Andrena curvungula only on bellflowers (bottom).
Male (left) and female (right) of Andrena florea.

English translation of the information panel in the Botanical Garden. Original German text: Dr. Barbara Ditsch, Mandy Fritzsche