Andy Sands / Female Blue mason bee (Osmia caerulescens) carrying pollen on its abdominal scopa (pollen carrying hairs) to a nest cell in an insect box, Hertfordshire, England, June.

Andy Sands / Female Blue mason bee (Osmia caerulescens) flying into an insect box, with mandibles covered in pollen, Hertfordshire, England, June.

Solvin Zankl / Common poppy bee (Osmia papaveris / Hoplitis papaveris) filling its nest with pollen and nectar, Bamberg, Germany.

Solvin Zankl / Poppy bee (Osmia papaveris / Hoplitis papaveris) leaving its nest which is lined with Common poppy (Papaver rhoeas) petal pieces. The animal leaves the frame. Bamberg, Germany.

Solvin Zankl / Two-coloured mason bee (Osmia bicolor) female covering nest with twigs and grass for camouflage, Witzenhausen, Germany, May.

Solvin Zankl / Two-coloured mason bee (Osmia bicolor) female covering nest inside snail shell with twigs and grass for camouflage, Witzenhausen, Germany, May.

Solvin Zankl / Two-coloured mason-bee (Osmia bicolor) female repositioning empty snail shell where she has her nest, Witzenhausen, Germany, May.

Solvin Zankl / Two-coloured mason bee (Osmia bicolor) female provisioning nest inside a snail shell with pollen and nectar, Witzenhausen, Germany, May.

Nick Upton / Female Red mason bees (Osmia rufa) collecting mud from the margins of a garden pond for sealing their brood cells in an insect hotel, Wiltshire, UK, May.

Nick Upton / Female Red mason bee (Osmia rufa) collecting mud from the margins of a garden pond for sealing her brood cells in an insect hotel, Wiltshire, UK, May.