ARTHROPOD MUSEUM NOTES
Number 107; April 15, 2014; Jeffrey K. Barnes
Genus and species: Demodex folliculorum (Simon)
Follicle mites live exclusively in human hair follicles. They are minute in size, about 0.3 millimeters long, worm-like, and they have rudimentary legs. They can occur anywhere on the face, around the ears, and sometimes elsewhere, but they are most common on the forehead, cheeks, and nose, particularly in the nasolabial folds (the so-called "laugh lines" that run from the sides of the nose to the corners of the mouth). They prefer oily skin. After mating in the follicle opening, females burrow into follicles and lay eggs. They feed on cell contents from the follicular epithelium. The young mature in six days. The entire life cycle lasts about two weeks. Follicle mites do not defecate. They store waste in large gut cells. When they die, the waste is released from their disintegrating bodies. They have no proven detrimental effects on humans, although studies have linked high populations of mites to cases of acne, rosacea, and the eye inflammation blepharitis. In one study of 370 volunteers from Western New York, 24 percent of the individuals were infested with follicle mites. Older individuals were more likely to be infested that younger individuals, and the rate of infestation in healthy skin reaches 100 percent in elderly people.