Biology Reference
In-Depth Information
Mites
Mites and ticks (the subclass Acari) form part of the
Arachnida, a major class of arthropods. Unlike insects,
they have no antennae, wings or compound eyes, are
usually 8-legged and possess chelicerate mouthparts
adapted for biting or piercing. The body is composed of
a gnathosoma, which bears a pair of sensory palps
(pedipalps) and paired chelicerae, and a sac-like
idiosoma with no obvious segmentation; they are thus
readily distinguished from other arachnids that have the
body divided into a distinct cephalothorax and a usually
(but not spiders) clearly segmented opisthosoma. The
respiratory system in the Acari often includes a pair of
breathing pores, also known as stigmata; their position
on the body, or their absence, forms a basic character for
naming the various acarine orders.
Unlike members of other arachnid groups, the Acari
includes many phytophagous species, mainly in the
order Prostigmata. The chelicerae of most prostigmatid
mites are needle-like and are used to penetrate plant
cells; also, the idiosoma is subdivided by a subjugal
furrow into the propodosoma and the hysterosoma, each
region bearing two pairs of legs. The body and limbs of
a mite are adorned by various setae, the arrangement
and characteristics of which are of considerable value in
the classification and identification of species.
Development from egg to adult usually includes a
six-legged larva and two or three eight-legged nymphal
stages: proto-, deuto- and tritonymphs. Larvae and
nymphs are generally similar in appearance and habit to
adults but are smaller and sexually immature.
Many phytophagous mites are free-living but others
(notably members of the Eriophyoidea) inhabit
distinctive galls formed in response to toxic saliva
injected into host plants during feeding. A few species
are important vectors of plant virus diseases.
Classification of mites
Subclass ACARI
Superorder OPILIOACARIFORMES
Order Notostigmata
weakly sclerotized, brightly coloured, harvestman-like mites, with four pairs of
hysterosomal stigmata
Superorder PARASITIFORMES
Order Tetrastigmata
a small group of large, heavily sclerotized mites
Order Mesostigmata
a large, diverse group of mites, including many predacious species
Order Metastigmata
ticks
Superorder ACARIFORMES
Order Prostigmata
an extremely varied group of minute to large, usually lightly sclerotized mites,
including many phytophagous species
Order Astigmata
soft-bodied, lightly sclerotized mites without stigmata
Order Cryptostigmata
dark, strongly sclerotized mites, often known as oribatids or 'beetle mites'
Brief details of the main groups containing pests of ornamental plants are given below:
Prostigmata : mites with the stigmata placed between
the chelicerae, and often with one or two pairs of sensory
hairs (trichobothria) on the propodosoma.
Family Phytoptidae (p. 405); prodorsal shield
bearing three or four setae; feather-claw simple:
genus Phytoptus .
Superfamily Eriophyoidea: minute, sausage-shaped
or pear-shaped mites with two pairs of legs, each leg
terminating in a branched feather-claw; body with a
distinct prodorsal shield; hysterosoma annulated with
a dorsal series of tergites and a ventral series of
sternites.
Family Eriophyidae (p. 406); similar to the
Phytoptidae but prodorsal shield bearing two or no
setae; feather-claw either simple or divided.
Subfamily Cecidophyinae
- elongate mites
without
prodorsal
shield
setae:
genus
Cecidophyopsis .
Subfamily Eriophyinae
-
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