Tick - small,
often microscopic chelicerate that, along with the tick, makes up the
order Acarina; it is also related to spiders. The unsegmented mite body
is typically oval and compact, although a few, mostly parasites, are
elongated and wormlike. There are four pairs of legs. The movable head
is attached to the body by a hinge. There are four stages in the life
cycle: egg, larva, nymph, and adult. The thousands of different mite
species are worldwide in distribution and occupy diverse habitats, including
plant galls, mosses, other animals, and surface litter or upper layers
of the soil. One group, the water mites, has returned to an aquatic
environment, both fresh- and saltwater. An anchoring structure in the
tick's mouth enables it to embed its entire head under the skin of the
host, where it sucks the host's blood. If a tick is pulled off the host,
the head usually remains embedded in the skin. Members of the family
(Argasidae) of soft ticks, with a membranous outer covering, hide in
crevices and come out at night to suck blood. Hard ticks (family Ixodidae),
which have thickened outer plates made of chitin , remain attached to
the host for long periods. Each species needs three different hosts
to complete its life cycle. Typically the larval stage will feed on
small reptiles, birds, or mammals; the nymph stage will parasitize larger
vertebrates; and adults will parasitize large herbivores and livestock.
The adult of the ixodid species Ixodes dammini, the vector of Lyme disease
in the E United States and Canada, usually chooses deer as its host
( I. dammini of all stages will feed on humans). The closely related
I. pacificus, which transmits Lyme disease and Rocky Mountain spotted
fever in the western states, prefers livestock in the adult stage. Ticks
can sometimes harbor more than one disease organism at a time. Mites
and ticks belong in the phylum Chelicerata , class Arachnida, order
Acarina.
DAMAGE AND CONCERN
Mites eat plant
or animal substances, decaying organisms, and humus, and also infest
stored food products such as cheese, meat, grains, and flour. The spider
mite, or red spider, which is a mite and not a spider, feeds on plants
and is destructive to crops. Many mites are parasitic on other arthropods,
on mollusks, or on vertebrates. Mange and scabies mites lay their eggs
in the skin and cause irritation in humans and fur-bearing animals.
Other species are parasitic on the skin of birds and reptiles, and some
live in the respiratory channels of birds and mammals. Chiggers, the
larvae of harvest mites, transmit the organism that causes scrub typhus.
Fowl mites feed on the blood of poultry. The larger members of the order
Acarina, the ticks, are all parasitic in at least one developmental
stage; most parasitize mammals and birds although some have reptilian
and amphibian hosts. Tick-borne diseases of livestock (e.g., babesiosis
, anaplasmosis ) are of great economic significance. Ticks transmit
Rocky Mountain spotted fever , tularemia , Lyme disease , equine encephalitis
, several forms of ehrlichiosis , and other diseases.
Columbia Encyclopedia,
Sixth Edition, Copyright (c) 2003.

Aries
Pest Control, Inc.