Oak Leaf Gall Mite

P. herfsi has been recorded in Czechoslovakia, Egypt, Australia, northern India, and the United States. It is a regulated pest in Germany.

Newly emerged and mated females inject a neurotoxin-containing saliva into their hosts, which paralyzes the host and enables the gravid female mites to feed on the host's hemolymph. The posterior portion (opisthosoma) of the female enlarges as its progeny develops inside, and, within a few days, up to 250 adult mites emerge from the gravid female. Males emerge before the females, position themselves around the mother's genital opening, and mate with emerging females. Then, mated females disperse to find new hosts. These mites often are dispersed by wind, and when they land on vertebrate hosts, they attempt to feed, resulting in the bites. A life cycle can be completed within seven days, and progeny emergence can be extended to 15 days. The mites' reported hosts have included Anobium punctatum, the pink bollworm, Grapholita molesta, Tineola bisselliella, Apis cerana (Asiatic honey bee), periodical cicadas, and various pests of stored grain, as well as humans and their pets. Their usual hosts in the United States are oak midge larvae. Cooler, more moist conditions favor its population growth. Outbreaks of attacks on humans in the United States have been attributed to fluctuations in the supply of both oak midge larvae and periodical cicada eggs.