Red square, blue circle, yellow triangle: The sequence can be traced back to the color and shape theory of the Bauhaus artist Wassily Kandinsky.

Grellroth, a novelty concrete producer in Krefeld, Germany, adopts the artist’s style in the design of bee hotels it casts from self-consolidating concrete mixes, dosed with weather-stable Lanxess inorganic pigments.Marketed as “beehaus,” the hotels have edge lengths of around seven centimeters and are available as a red cube, blue cylinder or yellow pyramid.

“The red hotels are always the first to be filled,” notes Gellroth Managing Director Diana Schmidt-Rothmeier. “Developing and manufacturing the polyurethane molds for this purpose was a challenge in itself, because the necessary draft angles in the narrow tubes require a certain expertise.”

Insect hotels are usually made of wood or plant stems, whose tendency to splinter can injure bees and their delicate wings, she adds. The advantage of concrete as a material—especially in self-consolidating mix form—is that the nesting enclosure walls are smooth.