Quick Dips

Computerising Mites on Video

Studying the behaviour of animals can give us a lot of useful knowledge and insight as to how they interact with their environment. When the animal you're dealing with is approaching the microscopic level of size, however, making observations can be tricky -- the practical problems of objectively describing what a small, fast-moving speck is doing are fairly obvious.

Lincoln University entomologists Mike Bowie and Sue Worner have developed a way of addressing this problem. By confining their subjects, two species of spider mites less than half a millimetre long, to a small "arena" which is lit from below, Bowie and Worner can record the mites' movements by means of a video camera. The data can be immediately sent to a computer for display and analysis in real time, or stored for later use.

With lighting arranged so that the mite stands out clearly on the video, the image is then digitised into a 512 pixel-square format by a program called BUGSY. Computerised processing can work out whereabouts in the resulting picture the mite is, and once every second its position is recorded, allowing its path to be plotted accurately and its activity to be analysed statistically.

Each pair of points gives information on the mite's speed and direction of travel, and from this basic information, more complex parameters can be calculated. From the patterns which arise, it is possible to determine some of the influences on behaviour exerted by different conditions.

The researchers believe their method is less laborious and more accurate than earlier approaches, but stress that it's an adjunct to more traditional styles of observation rather than a replacement.