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ACARINA Mites (Contact) Please CLICK on
underlined links to view: [Key to Medically
Important Acarina] The Acarina are small to tiny
arachnids. The largest (e.g. fully gorged ticks) may reach a length of nearly
25 mm., while the smallest rarely exceed 0.25 mm. in length. The order has
many identified species, but specialists admit that this could represent less
than 20 percent of those that occur worldwide. Similar to the insects and
crustaceans, the species in nature occur in very large numbers. The body is
depressed dorsoventrally and serves for adaptation to their mode of life. The
head and abdomen are fused, producing a saclike appearance. In some species
the cephalothorax may be separated from the abdomen by a groove or furrow.
The body may be partially or completely by a shield-like structure. The mouth parts are located on the
anterior ventral surface. The eyes are either present or absent; when present
they consist of simple convex facet and are generally located on the margin
of the scutum or on folds on the ventral surface. The respiratory organs,
when present are connected to the exterior by means of spiracles. The
spiracles are generally on chitinized plates and may be either singly or in
pairs. Tracheae are absent in some
species where breathing id directly through the body wall. Sexes are distinct, the males usually
smaller than the females.
Reproductive organ openings are located on the ventral surface behind
the mouthparts. The digestive system
is a straight tube usually with many tubular branches. The anal opening may be either on the
ventral or dorsal side, but rarely at the posterior. There are many different habits among the mites. They consume mainly body fluids of their
host plants or animals or from decomposing organic matter. Many mites are free-living and predatory,
and many are also parasitic.
Parasitic mites have a great variety of life styles. For example, the ticks are external
parasites of animals, feeding on blood.
Some ticks burrow into the skin and cause itching and subsequent
infections. Other species are found
in the lungs of seals and monkeys.
Chiggers are free-living and herbivorous or predaceous as nymphs and
adults. Many species attack birds,
feeding on their scales and feathers or they may invade the lungs and hollow
bones. Some species attack stored
food products and pass over to humans working close by. Of great importance are the bloodsucking
mites that serve as intermediate hosts of human pathogens.
The identification of mite
species is continuously changing, as they are a difficult group to
study. The position of body hairs is
frequently used for diagnoses.
Acarina that are parasitic may be found primarily in the following
Suborders and Superfamilies: CLICK on following
Groups for Details of Importance
& Control
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Key References: <medvet.ref.htm>
Banks, N. A. 1915. The Acarina or mites. U.S. Dept. Agr. Rept. 108. Bishopp, F. C. 1935. Ticks and the role they play in the
transmission of diseases. Rept.
Smithsonian Inst. for 1933: pp 389-406. Bishopp, F. C. & H. L. Trembley.
1945. Distribution of certain
North American ticks. J.
Parasitology:: 31-1-54. Bishopp, F. C. & H. P. Wood.
1913. The biology of some
North American ticks of the genus Dermacentor. Parasitology 6:
153-87. Cooley, R. A. 1942. Determination of Ornithodoros species. In:
Symposium on relapsing fevers in the Americas. Am. Asoc. Adv. Sci. Pub. 18:
77-84. Ewing,
H. E. 1926. Key to the known adult trombiculas (adults of chiggers) of the
New World with descriptions of two new species (Acarina,Trombidoidea) Ent.News 37: 111-13. Ewing,
H. E. 1944. The trombiculid mites (chigger mites) and their relation to
disease. J. Parasitology 30: 339-65. Matheson,
R. 1950. Medical Entomology. Comstock Publ. Co, Inc. 610 p. Service, M. 2008. Medical Entomology For Students. Cambridge Univ. Press. 289 p |