New garden species

Osmia caerulescens (Blue mason bee)♀︎

Nepeta sp.

Last update: 7 June 2021


LOCATION: Krimpen aan den IJssel, garden


This bee caught my attention although it was rather small. 

Blue mason bee ♀︎ (Osmia caerulescens) on Nepeta spec.

The bee flew among the flowers below the bee hotels and I noticed immediately that this was something different from the usual roaming guests.
The stout shape and enormous head made make it look quit special. After determination I found it to be a female Hoplitis leucomelana, a rare bee in the Netherlands, which is often an indication that the determination was incorrect. But after checking and double checking the name remained. So I called in the help of the bee experts on forum, and for sure it was another bee 😔: the Blue mason bee (Osmia caerulescens). Thanks to Flor Rhebergen for providing the name.

The determination error was that I regarded the pollen brush hairs as white, where the key [4] regards them as black….  😳 ok… 🧐

Blue mason bee ♀︎ (Osmia caerulescens) black pollen brush hairs

I still have a little difficulty calling the brush black but after looking more closely there are black hairs visible. The photograph isn’t sharp, potentially there are also lightly colored pollen in it
The blue glow and the enormous head are clearly distinquishing chracteristics when seeing the bees side by side on photographs.

Blue mason bee ♀︎ (Osmia caerulescens)
Blue mason bee ♀︎ (Osmia caerulescens)

Although this is a rather rare bee [3], I still like it and think it is very nice looking. For me it is not necessary for an insect to be rare, the main attraction is that this, for me new, species came to the garden at all, a new garden species that gives me the feedback that my little garden project produces some effect which in turn provides me with a boost of positive energy to continue my efforts 😅


The female is a regular guest on the Nepeta plants where she, as far as I’ve been able to observe up til now, only drinks nectar.

Blue mason bee ♀︎ (Osmia caerulescens) on Nepeta sp.


1 Nederlands Soortenregister

2 Forum, pag: Topic page:

3 Reemer, Menno. "Basisrapport voor de Rode Lijst Bijen", EIS Kenniscentrum Insecten, Leiden

4, "De Nederlandse bijen en hun relaties, overzicht van in Nederland en Vlaanderen voorkomende solitaire en sociale bijen (Apidea s.l.)"

Leave a Reply

Your email address will not be published. Required fields are marked *