This bee-fly flew around stacked firewood, looking for nest holes of bee host species.
The stacked firewood was heavily infested with woodboring insects. These produced lots of wood frass,
visible as the fine wood-dust accumulated on the bark. The bee-fly was tapping
the tip of her abdomen into the frass, a behaviour similar to that of other beeflies - but normally
the material is sand, not wood frass! The functional significance of this behaviour is obscure,
but might it be to camouflage the odour of the eggs to be oviposited in the nest of the host?