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The
Chelicerata includes spiders and scorpions, mites and ticks, horseshoe
crabs, daddy-longlegs, and extinct "sea-scorpions", to name a
few. It is the second most prominent order of terrestrial arthropods,
after the uniramians. Most of its marine representatives are extinct,
but were prominent in the Paleozoic and included some fearsome
predators.
Chelicerates occupy a variety of roles in the ecology of
marine systems and on land as well. While many spiders build webs,
others do not, but instead ambush prey as it passes by. This is also the
tactic used by scorpions, another group of chelicerate predators. |
The predatory habits of
these critters helps to control insect populations in many parts of the
world.
Some arachnid chelicerates are parasites, such as ticks and
mites. They live upon the bodies of other animals and feed on the blood,
skin, or hair. Some of these carry diseases, which they pass on to the
host when they feed. Still other chelicerates are tiny organisms which
feed on detritus, the bits of decaying matter that accumulate on and
below the ground. The first terrestrial chelicerates are believed to
have been detritus feeders.
Parental care is not common among the chelicerates, but
some scorpions will carry their young on their backs for a time. In most
cases, however, no such care is provided, and the young must fend for
themselves from the time they hatch. Survival is then dependant on the
fact that large numbers of eggs are produced at a time, and it is likely
that at least a few will survive. |
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