Animal Diversity Web

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

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

• Breeding season

  Reproduction occurs throughout the year.

• Average number of offspring

  20-24

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: 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.

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.

Con­ser­va­tion Sta­tus

Hair fol­li­cle mites are com­mon world­wide.

• IUCN Red List

  No special status

• US Federal List

  No special status

• CITES

  No special status

Con­trib­u­tors

Aisha Rush (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, Tanya Dewey (ed­i­tor), An­i­mal Di­ver­sity Web.

Ref­er­ences

1994. "Mites: Eco­log­i­cal and Evo­lu­tion­ary Analy­ses of Life-His­tory Pat­terns.". New York: Lon­don:Chap­man and Hall.

Baker, E. 1952. An In­tro­duc­tion to Ac­arol­ogy. New York: The MacMil­lan Com­pany.

Prasad, V. 1988. Mites: A Bib­li­og­ra­phy. Michi­gan: In­dira Pub­lish­ing House.

Ver­cam­men-Grand Jean, P. 1968. The Chig­ger Mites of the Far East. Wash­ing­ton: U.S. Army Med­ical and De­vel­op­ment Com­mand.

Wool­ley, T. 1988. Ac­arol­ogy: Mites and Human Wel­fare. New York: Wiley In­ter­science.