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Blattodea:
cockroaches
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Characteristics
The
general form of cockroaches varies little, however their size
can range from only a couple of millimetres in length up to
70 millimetres for the Giant Rhinoceros cockroach from Northern
Queensland. There are just over 400 species of cockroaches
in Australia out of 4000 worldwide, the best known being the
introduced pests which commonly inhabit houses, restaurants
and sewers. All cockroaches have the following characteristics:
- Oval
and flattened body shape
- Thorax
covered by a large plate (the pronotum),
which extends partly over the head
- 2 pairs
of membranous
wings when present. Forewings are more sclerotised
than hind wings. Wings are folded left over right when at
rest
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Cockroach
Lifecycle |
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Life Cycle
Cockroaches
have incomplete metamorphosis. Most species of
cockroaches lay eggs in an ootheca
(egg case) that is either deposited on or under suitable substrate,
or carried attached to the genital region. The egg stage lasts from
a few weeks to a few months. The young are active from hatching
and resemble the adults but are usually lighter in colour and lack
wings. The young cockroaches develop through a number of nymphal
instars,
which may range from 2 to 12 depending on the species and may take
from a month or so up to 12 months to reach maturity. Some species
may live for several years.
Feeding
Much of
the feeding habits of native Australian cockroaches is unknown,
but it is likely the majority are omnivorous.
Some species are known to feed predominantly on rotting wood while
some species harbour symbiotic
gut Protozoa that aids in cellulose
digestion. The introduced domestic species appear to eat almost
anything.
Habitat
Cockroaches
in Australia are widespread and adapted to both wet and dry environments.
Most species are nocturnal
and ground dwelling and are usually found hiding during the day
in crevices, under bark, rocks or logs and in burrows. Some species
may occur on plants or in litter and some also occur solely in caves
or ant nests. Others are associated with human habitation.
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