Supplementary material S4: Interaction behaviour.

<p>A short video extract of three <em>Varroa </em>mites interacting with one another. The cause of this interaction is unknown but has been seen on a handful of occasions where mites come into close contact with one another and appear to be become &lsquo;stuck&rsquo; on each other&rsquo;s legs. This causes them to roll around the petri-dish until they become dislodged from one another. The vibratory signal produced by this interaction can be heard in this video. The soundtrack of the video is, again, the signal coming from the accelerometer that can be seen secured to the petri-dish.</p>