Pyemotes herfsi, also known as the oak leaf gall mite or itch mite, is an ectoparasitic mite identified in central Europe in 1936 and subsequently found in India, Australia, and the United States. The mite parasitizes a variety of insect hosts and bites humans, causing red, itchy, and painful wheals (welts). The mites are barely visible, measuring about 0.2 millimeters; their great reproductive potential, small size, and high capacity for dispersal by wind make them difficult to control or avoid.