While walking through a park in Lisbon, Portugal, I crossed paths with a stunningly tiny, metallic insect: the cucumber small carpenter bee (Ceratina cucurbitina). Unlike large carpenter bees that drill into solid timber, this solitary species uses its mandibles to excavate nests inside the soft, pithy stems of dead plants like mullein, elderberry, and brambles. Leaving old stalks intact in gardens is vital for their survival, as both males and females rely on these hollow tunnels to nest and hibernate. Inside, females construct 8 to 9 brood cells with a precise order: inner cells near the base produce mostly females, while outer cells near the entrance are male-biased. The cucumber small carpenter bee is the most common small carpenter bee species found across Europe, and a vital pollinator.