Scientific note: Bombus terrestris workers can use nesting box of Osmia bicornis to create unusual above-ground colony

Abstract

Bombus terrestris are known for nesting underground. Here, we describe observations of an unusual, opportunistically built above-ground nest of buff-tailed bumblebee. The B. terrestris nest contained six workers and 14 cocoons with pupae at various stages, two empty pollen pots and nine reed tubes also used as nectar/pollen storage pots. Bombus terrestris workers used a wooden nesting box with reed tubes, which was designed as a nesting aid for solitary bees (Osmia bicornis). In our opinion, the most likely scenario is that this was an unintended consequence of removing commercial Bombus nests from the apple orchard in the middle of the day, so foragers had no place to return to and settled in the nearest possible place/shelter. This is a great example of the high flexibility of bumblebees in terms of available (anthropogenic) nesting sites and may suggest that microcolonies can also occur in nature.