By Aisha Rush
Geographic Range
These mites are distributed worldwide as commensals of humans. It is unknown from what region they originated, they have been associated with humans throughout their evolutionary history. They inhabit the hair follicles of most if not all humans. They infest areas around the nose, in the ear canals, and around the eyelids. (Woolley 1988)
Biogeographic Regions:
nearctic 
(native ); palearctic (native ); oriental (native ); ethiopian (native ); neotropical (native ); australian (native ); oceanic islands (native ).
Other Geographic Terms:
cosmopolitan .
Habitat
The habitat for this mite is inside the hair follicle of a human. (Baker 1952, Woolley 1988)
Physical Description
These are weakly colored mites--probably to enable them to blend in with their environment (the human skin). They are also very small, ranging in length from .10 to .39mm. They are cigar shaped with eight short and stubby legs. Like most mites, they exhibit no segmentation and have a completely fused cephalothorax and abdomen. They also have simple eyes. The mouth or head region contains chelicerae (which helps to classify them in the subphylum chelicerata) that are greatly reduced, reducing the gnathosoma to a stubby structure. This particular mite does show sexual dimorphism in that the female mite appears to be shorter than the male with a more rounded body. The male tends to be a little longer than the female and much more slender in appearance. (Baker 1952, Woolley 1988)
Reproduction
Reproduction occurs throughout the year.
The entire life of the mite is spent on the host. They cannot be obtained from any other animal besides humans. Reproduction occurs through internal fertilization. The abdomen of both male and female mites bear genital openings. Their life cycle is usually complete in 18-24 days. The adult female mite lays 20-24 eggs in a hair follicle. These eggs are nourished and incubated by the cells surrounding them within the follicle. After the eggs hatch and the nymphs emerge, they are similar to the adults but only have six legs rather than eight. The remaining two legs grow during as the nymph develops into an adult (anamorphism). (Baker 1952)
Key reproductive features:
year-round breeding ; sexual ; fertilization (internal ); oviparous .
Behavior
Much of their behavior is expressed through their eating and reproductive habits.
Food Habits
Demodex folliculorum are housed in hair follicles; they derive their nourishment from the cells of the host. Their main source of food is human glandular secretions within these follicles. It is also here where the larvae are nourished and grow into the adult form of the mite. (Baker 1952)
Primary Diet:
carnivore (eats body fluids).
Animal Foods:
body fluids.
Economic Importance for Humans: Negative
Some people may have allergic reactions to these mites. Such reactions may cause hair loss or the development of acne.
Economic Importance for Humans: Positive
There is no specific harm to humans from these mites. Hair follicle mites share a commensalistic relationship with humans in that they benefit from their association with humans, but the host is unharmed.
Conservation Status
IUCN Red List: [link]:
Not Evaluated.
US Federal List: [link]:
No special status.
CITES: [link]:
No special status.
Hair follicle mites are common worldwide.
For More Information
Find Demodex folliculorum information at
Contributors
Aisha Rush (author), University of Michigan.
Tanya Dewey (editor), Animal Diversity Web, University of Michigan Museum of Zoology.
