The experimental setup.

<p>The choice arena was constructed from a Petri dish (Ø 9 cm) positioned up side down. An insect glue barrier (ig) divided the dish in two compartments that each contained an odor source (o) An opening at the bottom allowed for the connection of a cartridge containing the mites. The cartridge (c) was fitted to a vacuum pump. The vacuum gives rise to a radial airflow over the bottom of the choice arena, thus establishing two odor fields that extended from the odor sources to the cartridge. Arrows indicate air flow direction in the system.