Spiders and Harvestmen
Aphonopelma species
Description
Tarantulas are large, hairy spiders, 1 3/8" (33 mm) or more long, with a legspan up to 5 7/8" (150 mm). These spiders have 8 closely grouped eyes; the large middle pair are circular with 3 eyes on each side. Each leg has 2 claws at the tip and a tuft of hair underneath. There are microscopic bristles on the abdomen, which break off easily and can irritate the skin of small mice and other prey. Males have longer legs and are more active than females.
Warning
Tarantulas have venom that is used to kill prey, but there are no tarantulas in the world that are considered dangerously poisonous to humans. When threatened, all tarantulas will use their hind legs to kick hairs from the upper surface of the abdomen. These hairs cause a burning sensation when they contact sensitive skin or mucuous membranes.Food
Tarantulas feed mainly on insects and other invertebrates, but will take lizards and small mammals on occasion.Habitat
Tarantulas are usually found in open habitats; most of the species found in the U.S. are from arid regions.Range
Throughout the Southwest, into central California and as far north as southern Illinois in the Midwest.Discussion
Tarantulas are our largest spiders. They spend most of their life underground in a silk-lined burrow. They rest at the bottom by day; after dark they wait near the surface and pounce on insects and other small animals as they wander by. Seldom do they venture more than a few inches from the burrow entrance. They develop slowly, taking between eight and eleven years to reach maturity. Adult males leave their nests during breeding season and wander overland in search of receptive females. Males die soon after mating; in fact, even unmated males seldom live more than a few months after reaching adulthood. Most of the tarantulas encountered by people are males out looking for mates. Females on the other hand may live for many years as adults and can breed several times.Meal of the Living Dead
Fall is the time of year when
male tarantulas, having finally reached adulthood, come out of the
burrows in which they have lived for the first 5 to 12 years of
their lives. Their mission? To seek out females and mate with them.
A host of perils awaits the newly emerged male in the outside world,
not the least of which is the female herself.
Female
Power
Female tarantulas are doing what they usually do on
warm evenings: sitting in their burrows near the surface, waiting to
feel the vibrations of passersby. If the vibrations feel as if they
might come from a small animal such as a cricket or another spider,
she will rush out, grab the unsuspecting prey item and sink her
fangs into it. When a male tarantula approaches the burrow of a
female, he first tastes the silk that lies around the entrance. If
he detects a mature female in residence, he responds by drumming on
the surface with his legs and his pedipalps (the leg-like first set
of appendages, which are very long on tarantulas). The reason for
this drumming is to let the female know that he is interested in
mating -- and would rather not be mistaken for a meal by the larger
and always hungry female. When and if a female emerges, he continues
to drum as he approaches her. If she's receptive, she will raise up
the front end of her body and allow him to grab her fangs with the
hook-like projections on his forelegs. He then transfers his sperm
to her with his pedipalps.
That was the easy part -- the
difficult task still lies ahead: he must release her fangs,
disengage himself, and make a hasty retreat before she can overpower
him and eat him. Even if he successfully escapes from his big date,
the male tarantula is still not long for this world. Adult males
(mated or not) usually die before winter arrives.
Hairy
Meal
As if being eaten by your mate isn't enough to worry
about, the male tarantula must also be on the alert for predators
like owls, skunks, and foxes. If he detects the approach of a hungry
hunter, his most effective defense is to quickly use his hind legs
to kick some of the hairs off of his abdomen. The hairs dislodge
easily and are light enough to float into contact with the nose and
eyes of the approaching predator. On contact the hairs produce a
burning sensation. This line of defense works well against mammals
and birds, but there is another tarantula hunter out there that is
an even greater threat, and it is considerably smaller than the
spider: it is a wasp called the Tarantula Hawk.
Wasp
Feed
Tarantula Hawks are among the largest wasps in the
world; one North American species exceeds two inches in length. They
are handsome insects with metallic blue bodies and orange wings,
sometimes seen sipping nectar at flowers (particularly milkweeds) in
the early evening hours. Female Tarantula Hawks patrol low over open
country, searching for wandering male tarantulas or for the burrows
of females. When the wasp finds a tarantula, she lands and
approaches the spider directly. The spider assumes a defensive
posture, raising the front legs and baring the lethal-looking fangs.
Unfortunately for the spider, this posture also exposes its
underside to the agile wasp, which quickly darts under the spider
and stings it in a soft spot where the legs join the body. The sting
of the Tarantula Hawk contains a peculiar potion; it paralyzes the
spider almost instantly, but does not kill it. The "sleeping" spider
is then dragged to a burrow, pulled underground, and buried with a
single wasp egg attached to the outside of the body. When the egg
hatches, the maggot-like wasp larva has a huge fresh meal waiting
for it. The spider is still alive, its tissues undecayed and ready
for the wasp larva to devour. The voracious larva will even eat the
muscles and other "nonessential" tissue before consuming the
still-functioning organs.
So if you are out for a walk or a
drive on an early autumn evening and you happen to see a giant hairy
spider making his way over the ground, don't react with fear. Just
wish him the best of luck. With all the perils ahead of him, he's
going to need it.