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Tarantulas - Family Theraphosidae
Tarantula spiders are perhaps some of the most recognized (and
feared and loathed) Arachnids on the planet. They do enjoy,
however, a large group of aficionados as pet-keepers, breeders
and promoters. Unlike other exotic pets such as boa constrictors
and mountain lions, tarantulas do not squeeze to death or maul
their owners.
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Mexican Red-kneed Tarantula, Euathlus smithii
© 2006 John White, used with permission
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Tarantula is the
common name for a group of hairy, large spiders
belonging to the family Theraphosidae. There are
approximately 900 species worldwide. Tarantulas
hunt prey on the ground and do not spin webs
unless they live in a tunnel, in which case they
line their tunnel with web to catch wandering
prey. They mainly eat insects and other
arthropods, caught by speed or ambush. The
biggest tarantulas can kill animals as large as
lizards, mice, or birds. Most tarantulas are
harmless to humans, and some species are kept as
pets.
Like all arthropods, the
tarantula is an invertebrate that relies on an
exoskeleton for muscular support. A tarantula’s
body consists of two main parts, the prosoma or
the cephalothorax (the former is most often used
because there is no analogous "head") and the
abdomen or opisthosoma. The cephalothorax and
opisthosoma are connected by the pedicle or what
is often called the pregenital somite. This
waist-like connecting piece is actually part of
the prosoma and allows the opisthosoma to move
in a wide range of motion relative to that of
the cephalothorax.
Depending on the species, the body length of
tarantulas range from 1-4 inches, with 3 to 12
inch leg spans. The largest species of
tarantulas can weigh over 90 grams (3 ounces).
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Red-kneed Tarantula, Brachypelma smithi
Gerald and Buff Corsi © California Academy of Sciences
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Red-kneed Tarantula, Brachypelma smithi
Gerald and Buff Corsi © California Academy of Sciences
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Goliath Bird-eating Tarantula, Theraphosa blondi
© 2006 John White, used with permission
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The eight legs, the two
chelicerae with their hollow fangs, and the
pedipalps are attached to the prosoma. The
chelicerae are two single segment appendages
that are located just below the eyes and
directly forward of the mouth. The
chelicerae contain the venom glands that
vent through the fangs. The fangs are hollow
extensions of the chelicerae that inject
venom into prey or animals that the
tarantula bites in defense, and they are
also used to masticate (chew). These fangs
are articulated so that they can extend
downward and outward in preparation to bite
or can fold back toward the chelicerae as a
pocket knife blade folds back into its
handle. The chelicerae of tarantulas
completely contain the venom glands and the
muscles that surround them and can cause the
venom to be forcefully injected into prey.
The pedipalpi are two six segment appendages
connected to the thorax near the mouth and
protruding on either side of both
chelicerae. In most species of tarantula the
pedipalpi contain sharp jagged plates,
called the coxae or maxillae, which are used
to cut and crush food. As with other
spiders, the terminal portion of the
pedipalpi of males function as part of its
reproductive system. Male spiders spin a
silken platform on the ground onto which
they release semen from glands in their
opistoma. Then they insert their pedipalps
into the semen, absorb the semen into the
pedipalps, and later insert the pedipalps
(one at a time) into the reproductive organ
of the female, which is located in her
abdomen. The terminal segments of the
pedipalps of male tarantulas are larger in
circumference than those of a female
tarantula.
Tarantulas, like almost all other spiders,
have their spinnerets at the end of the
opisthosoma. Unlike spiders that on average
have six, tarantulas have two or four
spinnerets. Spinnerets are flexible tubelike
structures from which the spider exudes its
silk. The tip of each spinneret is called
the spinning field. Each spinning field is
covered by as many as one hundred spinning
tubes through which silk is produced. This
silk hardens on contact with the air. |
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Common Tarantula
George W. Robinson © California Academy of Sciences
Tarantulas can make good pets. Many
species can be purchased as juveniles for
$20-$50. A terrarium with an inch or two of
damp ground coconut fiber, or a mixture of
soil and sphagnum moss (but not with cedar
shavings as they are toxic to many spiders)
on bottom provides an ideal habitat.
(Burrowing tarantulas will require a much
deeper layer.) Ambient temperature and
humidity vary by species, with most thriving
between 75 degrees and 80°F (24 to 27°C) and
between 40% and 80% humidity.
Tarantulas can be fed a variety of foods.
Tarantulas should not be fed vertebrates on
a regular basis as the calcium in the bones
will cause complications during molting and
may kill the tarantula. A tropical roach
colony is a good way to maintain a food
supply for a number of tarantulas. The
discoid cockroach and death's head cockroach
in particular are very easy to care for and
will not infest your home if they escape.
The death's head cockroaches can be kept in
an aquarium with no lid since they cannot
climb glass and don't fly. Maintaining a
colony of death's head cockroaches only
requires keeping them in the dark, feeding
them a handful of dog food every couple of
weeks and misting them with water every day
or two.
-- Adapted, with trepidation, from Wikipedia
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