Plants as building material for wild bees

Depending on the genus and species, bees use different materials such as clay, sand grains, saliva, tree resin, wood, flower petals, plant hairs or "plant mortar" made from chewed leaves when building their nests.

The most unusual strategy is probably that of leaf-cutter bees. They build their cigar-shaped nests in above-ground cavities. The nest consists of round leaf sections that they cut out of the leaves of certain plants, such as roses, using their mouthparts. Inside, the nest is again divided into individual brood chambers by pieces of leaves. At the end, a thick stack of circular and perfectly equal-sized leaf discs closes off the entrance.

Our most common species is the Willughby's leaf-cutter bee, which likes to forage on legume flowers (Fabaceae), such as restharrows (Ononis) and Lotus, but also on other flowers.

Image captions:
Willughby's leaf-cutter bee cuts out circular pieces from leaves.  
From these it builds cigar-shaped nests in cavities. The leaf moisture delays the drying out of the larval food.
The nest entrance is also closed with leaf discs.  
Male (left) and female (right) of the Willughby's leaf-cutter bee (Megachile wiillughbiella).

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