There are good mites, and bad mites, and many that are indifferent, but not many mites that are our friends. The Phytoseiidae (Acari: Mesostigmata), however, are our friends. This is because we share a common interest: spider mites (many of which are really bad mites). The species pictured above belongs to the type genus of the family: ‘Phyto’ (Greek for plant) and ‘seius’ (Greek for one who moves to and fro, or shakes). The generic name perfectly captures the Gestalt of the family: they are mites that scurry across leaves looking for other mites to eat. This species was named for (Big) Peter O’Reilly of OReilly’s Guesthouse in Lamington National Park, Queensland. Although Peter preferred birds, he was always supportive of scientific research, even on mites. This species lives on the leaves of rainforest trees in the canopy of Lamington National Park. Peter seemed delighted that I named the mite for him, but Peter was never less than polite, so he may have been humouring me.
O’Reilly’s Leaf-Roamer may or may not be of help to us in our long war with spider mites, but its cousin the Chilean Predatory Mites (Phytoseius persimilis) certainly is. The common name may or may not be accurate. The species was first described from the Mediterranean Region by the great Belgian-French acarologist Claire Athias-Henriot, but it was a cosmopolitan synathrope long before it was described. Our agricultural systems are very favourable to spider mite outbreaks. Phytoseiulus persimilis is a specialist predator of spider mites, especially those that produce dense webs of silk such as the Two-spotted Spider Mite (Tetranychus urticae), a very bad mite. Although it tends to follow us around, good biological control requires using your predators at the appropriate time in the prey’s population cycle. Fortunately, nowadays you can buy boxes of Chilean Predatory Mites to sprinkle on your greenhouse crops, strawberries, and other crops to fend off damage by spider mites.