Friday, September 21, 2012

Tarantula

Linda Ellis sent me this picture of one of her hirsute neighbors.  If there was an Oscar for the most misunderstood spider, the tarantula would win hands down.  Its appearance evokes a response somewhere between fear and revulsion, even leading one to star in a movie as a villain.  All of these responses are unjustified.

This is the Texas (or Oklahoma or Missouri) Brown tarantula, Aphonopelma hentzi, a native of Southwest United States.  Although you commonly hear that they arrived in a bunch of bananas, it is a native species whose northern range includes a stretch from Colorado to southern Missouri and as far east as Louisiana.  A. hentzi is considered to be the predominant tarantula species in this range.*  


The brown tarantula is one of the most common species of tarantula thriving in the southern-most United States today. They can have a leg span greater than four inches and weigh more than 3 ounces as adults. The body is dark brown in color, varying both between moults and among individuals.

Although quite memorable when found, they are rarely encountered as their preferred habitat is dry rocky glades.  They spend the day in silk lined burrows, frequently abandoned rodent or snake burrows.  They do not build a capture web but extend silk strands outward to act as trip wires.  At night they emerge to hunt crickets and other insect prey.  Large tarantulas are said to kill small mammals and even birds.

Tarantulas will mature sexually after 7-12 years.  The males have longer legs and will strike out in August and September looking for females.  After mating they will usually die within a few months.  The females stay close to their tunnels so the tarantulas we see out and about are usually males.


Note small eyes- T. J. Morgan
Large wolf spiders are frequently confused with tarantulas.  Wolf spiders have much larger eyes and like other spiders, their fangs move laterally while tarantulas' fangs move vertically.  Unfortunately, viewing a spiders' fangs means you are extremely close and looking under its palps.


Wasp and its prey
Even a large hairy spider has enemies.  In addition to birds and lizards, they, like many insects are victims of parasitic "tarantula hawk"wasps of the Pompilidae family.  These wasps paralyze the tarantula with a sting and lay an egg on it.  It then drags the spider into a burrow or a crevice where the wasp larva consumes it. 


Fangs- amazingtarantulas.com
Now back to fear and loathing.  Although a Texas brown tarantula comes equipped with an impressive set of fangs, its venom has little effect on humans and is never fatal.  They bite only when attacked or roughly handled and a bite is usually no worse than a bee sting.  Since they are unlikely to bite when handled gently, some people keep them as pets as seen in Youtube pet videos.  Handling a house pet tarantula may be a bit much for some of us but it does show that they are generally docile.

They have a second line of defense which affects animals that are sniffing them or touch their undersides:
"New-world tarantulas (those found in North and South America) are equipped with urticating hairs on their abdomen, and will almost always throw these barbed hairs as a first line of defense. These hairs will irritate sensitive areas of the body and especially seem to target curious animals who may sniff these hairs into the mucous membranes of the nose. Some species have more effective urticating hairs than others." Wikipedia
Bottom view with fangs- T. J. Morgan

The fear of the tarantula dates back to the middle ages in Taranto, Italy where it got its name.  Its bite was said to produce severe pain, spasms and exhibitionism, and death.  The only cure was said to be wild dancing, the origin of the folk dance known as the tarantella.  Neither the bite nor the cure have been documented in modern times.

Finally, what about the movie star spider I mentioned above.  A tarantula named Thomas was induced somewhat reluctantly to crawl across Sean Connery's chest in the first James Bond movie, Dr. No.

The most comprehensive information is in this PDF.


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