Mites: Ecology, Evolution & Behaviour: Life at a Microscale - Paperbackby David Evans Walter (Author), Heather C. Proctor (Author) More than 40,000 species of mites have been described, and up to 1 million may exist on earth. These tiny arachnids play many ecological roles including acting as vectors of disease, vital players in soil formation, and important agents of biological control. But despite the grand diversity of mites, even trained biologists are often unaware of their significance. Mites: Ecology, Evolution