Temporal Change in the Density and Feeding Habits of a Terrestrial Red Mite, Balaustium murorum (Hermann), on a Building Roof

We observed the seasonal occurrence and foraging behaviors of a terrestrial red mite, Balaustium murorum (Hermann), on the roof of a building in Osaka and analyzed the stable isotope ratios in the mite and three prey species to study its feeding habits. On direct observation, the adult mites formed groups and fed on small insects and anthers that had fallen on the roof. When pollen of the grass Polypogon fugax Steud. was experimentally added to the roof surface, the adult mites fed more frequently than they did without the pollen. We measured the stable isotope ratios of C and N in the mite and three prey species, P. fugax, a plant louse (Psyliidae sp.), and a cyanobacterium (Hassallia sp.), and estimated the contribution of each to the mite. This showed that P. fugax made the largest contribution, about 50%, irrespective of the estimation method. From these results, we concluded that the pollen was the most important food resource for the mite, although it is an omnivore.