We investigated the effect of several acaricides on Varroa destructor by monitoring the rhythmic expansion of the sternum, followed by a strong flexion of the legs, initiated when the mite was placed in a dorsal side-down position, as an indication of a mite’s vitality. The pulses generated by the force of the rhythmic expansions had an average duration of 3.11s, force (amplitude) of 73μN, and frequency of 0.228Hz. These parameters remained constant for the first 10h of recording, whilst significant changes occurred after 15h. The rhythmic sternal expansion is an indication of a Varroa mite’s gravitational reflex, or attempt to return to an upright position; this reflex is observed in all invertebrates and vertebrates. The sternal expansion can be recorded for over 20h, or for as long as the Varroa mite remains alive, and the expansion stops as soon as the mite is placed in a normal, upright position. Proper function of the chain of proprioceptors, interneurons, motorneurons, neuromuscular junctions, and muscles of Varroa is required for the initiation and maintenance of such a behavioural motor pattern. Any deleterious effect of synthetic chemicals or natural compounds (acaricides) may have a direct effect on one or more of these links, thereby disturbing or even inhibiting the reflex. Topical application of 1.81×10 −3 mg/mite of amitraz completely inhibited the gravitational reflex within 60–70min for all mites tested. The volatile acaricides formic acid (13.83mg), thymol crystals (250mg), and Apiguard® (1000mg) eliminated the reflex within 10–35min. This bioassay, based on the gravitational reflex, could be a useful tool for accurate assessment of the acaricidal action of numerous compounds under laboratory conditions, saving money and time necessary to conduct field trials.