Flowering time is bee time

The flight time of solitary wild bees is often only a few weeks, depending on the flowering time of their forage plants. The small sallow mining bee (Andrena praecox), as a spring bee, is only on the move as long as the willow catkins are in bloom. They are followed by early summer bees and finally late summer bees, such as the heather colletes bee (Colletes succinctus).
Most species fly from April to June, when flower diversity and density are highest. This is also when the  large yellow-face bee (Hylaeus signatus) can be found on mignonette flower spikes. The males often appear shortly before flowering begins and then patrol the plants for weeks. The genus owes its name to the typical white to yellow "face mask". The females carry the pollen in a kind of goiter to the nest, where they spit it out again - a very original behavior for wild bees.

Image captions:
White mignonette (Reseda alba L.) from the Mediterranean region grows and blooms in our collection of summer annuals.
Wild mignonette (Reseda lutea L.) is a native wild plant. It thrives in low humus, loamy sandy and gravelly soils that are relatively sparsely vegetated.
Male (left) and female (right) of the  large yellow-face bee (Hylaeus signatus).

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