the goliath tarantula is not only one of the largest of the 35,000 species of spider — it can weigh up to 70 grams with a leg span of up to 10 inches — but is also among the least known.
goliath bird-eating spider is pretty harmless to humans, as are most species of tarantulas. They do carry venom in their fangs and have been known to bite humans when threatened, but the venom just causes swelling and mild pain for a few hours (like a wasp sting). Tarantula bites to humans are usually in self-defense and don't always contain spider venom - what is known as a "dry bite".
The most dangerous thing about the goliath bird-eater is its ability to flick urticating hairs from its body at any creature it perceives as a threat, including humans. This is not a species of tarantula you'd keep as a pet. The tiny, almost invisible hairs that it voluntarily sends floating through the air are extremely irritating to our skin, and can cause real problems if they got into delicate mucous membranes around eyes and mouth.
As hunters, tarantulas can be fearsome predators. Tarantulas don't have any special techniques, such as building intricate webs, or leaping great distances, for hunting their prey. They use good, old-fashioned stealth and strength, very much like wild cats. They sneak up on their prey and pounce on the unsuspecting victim, inflicting a fatal bite with venomous fangs.
One fascinating feature of goliath bird-eaters, as well as some other tarantula species, is their ability to make noise. We don't normally associate spiders with noise, like we do with dogs, cats, birds, etc. We are accustomed to seeing spiders silently, stealthily crawling across walls, floors, and the sidewalk. But when feeling threatened, the goliath bird-eater is capable of making a pretty loud hissing noise by rubbing bristles on its legs together. Called stridulation, it can be loud enough to be heard up to 15 feet away!
Portia
Unlike most jumping spiders, which prey on insects, Portia uses deception and mimicry to catch and eat other spiders. It is a cryptic spider and an aggressive mimic, meaning that it imitates something its intended victim finds harmless or even attractive. The mimicry is of two kinds: first, it resembles a fragment of litter detritus. This is a camouflage against other jumping spiders, that have good vision. This way, it can get very close and kill the other spider. Second, it shows a kind of behavioral mimicry: Portia enters a spider's web and creeps up on its victim almost imperceptibly, though it moves quickly when the wind blows. It then plucks the web to imitate a captured insect (much like the Pirate spider). Then, when the resident spider approaches, Portia lunges in for the kill.
Portia preys on just about every kind of web-building spider, if it is from 10% up to double its own size. It varies its web signals to suit its specific victim. If it encounters a new spider species, it tries different signals rather randomly. Should one signal elicit a response from the victim, Portia will stop the random signals, and focus on the successful one. [1] Portia fimbriata has been observed to perform vibratory behavior for three days until the victim decided to investigate.
Unlike other jumping spiders, Portia sometimes builds a web which it fastens to the web of a future victim. Should the web catch insects, Portia will wait for the other spider instead of feeding on the insect.
To make the accurate vision necessary for such complex behavior possible, they employ a two-lens camera eye. With this system, they can see as clearly as a pigeon, but only a minute piece at a time. They are, for example, not able to discern the shape of a praying mantis, because it is too big for its field of vision. They have six eye muscles to move the field of vision around.
Basicly, its smart as hell.
