Agriculture Reference
In-Depth Information
The respiratory system varies considerably.
Mites with a tracheal system have spiracular
openings (stigmata) whose number and position
on the body may vary from order to order. Mites
that lack a tracheal system effect gaseous ex-
change thorough their integument.
The reproductive organs are located mid-
ventrally within the idiosoma, their exact posi-
tion varying considerably. In some mites they lie
close to the tip of the hysterosoma (i.e. they
occur distally); in others they may occur immedi-
ately just behind the gnathosoma at the anterior
part of the propodosoma (i.e. they occur proxi-
mally). In eriophyid mites, they are located at the
anterior part of the hysterosoma, just behind the
coxae and, in females, are concealed by a distinc-
tive flap (genital flap), the features of which (mi-
croscopically) are often of taxonomic value.
DEVELOPMENT AND GROWTH
Most mites develop through an egg stage, a 6-
legged so-called 'larval' stage and one, two or
three 8-legged nymphal stages: protonymphs,
deutonymphs and tritonymphs, respectively.
There are notable exceptions, for example: (a) in
the superfamily Eriophyoidea there is no larval
stage; also, the adults and nymphs have just two
pairs of legs; (b) in the family Tarsonemidae (or-
der Prostigmata) the 6-legged larva, when fully
fed, typically develops to adulthood through a
sedentary and non-feeding, pupa-like (quiescent
nymphal) stage that is retained within the
bloated, cast-off skin of the larva - this is remi-
niscent of the puparium found in certain Diptera.
CLASSIFICATION OF THE SUBCLASS ACARI
Table 2 shows a relatively simple classification
which maintains names familiar to many agricul-
tural zoologists (for clarification, frequently used
alternative names are indicated). Features of the
main groups of mites of agricultural or horticul-
tural significance in northern Europe are sum-
marized below.
Several classifications, often based partly on
the location on the body of a pair of breathing
pores (the stigmata), have been proposed for
mites; these include various combinations of
superorders, orders and suborders. Mites (often
cited as the Acarina) have also been regarded
merely as an order within the Arachnida.
ORDER MESOSTIGMATA
A large, diverse group of mites, including many
predacious species, most inhabiting soil or de-
caying organic material; a single pair of stigmata
sited laterally or dorsolaterally, close to coxae
II-IV; pedipalps 5-segmented; hypostome
without teeth; ocelli absent. Most species are
free-living but some are adapted for life as para-
sites of animals. Adults 0.2-2.0 mm long.
1. Family DERMANYSSIDAE
Oval or egg-shaped mites with, in females, either
a divided or an undivided dorsal shield; if divided
then the posterior section minute; dorsal shield
with more than 30 pairs of setae; chelicerae often
very long and needle-like. Obligate parasites of
vertebrates, especially birds.
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