From Nookipedia, the Animal Crossing wiki
The Tarantula (タランチュラ, taranchura) is a rare insect in the Animal Crossing series. It is worth 8,000 Bells. They are found on the ground, between 7 pm and 4 am, between June and August. They can be difficult to catch, like the Scorpion and Bee, as well as harmful - however, they do not attack the player unless he or she is carrying a net, and, unlike the Bee, the Tarantula does not leave a mark. If startled by rapid movement (whilst holding the net), in the same fashion as the Scorpion, it will attack (presumably bite) the player, causing the player to be momentarily stunned before fainting, which then leads to the player waking up in front of his or her house. If the player is not carrying the net whilst a quick movement is made near the Tarantula, like many other bugs in the game, it will move away from the player. It is not to be confused with the Spider.
Catching the tarantula
The Tarantula is harmful and should be avoided, unless the player is trying to catch it. It is suggested that the player does not equip the net during the hours the Tarantula is available, to avoid being "bitten" or "poisoned." It can jump over holes dug in the ground, as well as off cliffs and up onto the lower part of ramps joining the upper section of town to the lower part (in City Folk).
Upon approaching the Tarantula, the player should pull out the net and catch it like any other insect - though missing it the first time will prove fatal. An easy place to catch the Tarantula is just on the ramp of a slope in City Folk, just where it cannot jump up but where the net can also hit the ground. This makes the Tarantula run into the wall, and keeps it steady for the player to catch. In Animal Crossing: Wild World, the Tarantula is more noticeable by the sound it makes - scratching on the ground. In Animal Crossing: City Folk, it makes a lot less noise as in previous installments. It is much harder to catch in Wild World than in City Folk due to the lack of slopes.
There is another way to catch it. The player should pick an acre and walk as slowly as possible around it with the net equipped. There should be an open building nearby, not to avoid a Tarantula, but to reset bug locations. In other words, it might spawn a Tarantula. When the Tarantula appears, the player should creep towards it. It is easier to catch if the bug comes to a complete halt. It does not matter what direction the player is facing. When the position seems right, the player should swing the net. One can also slowly approach from behind to avoid its being startled by the player's presence and then swing the net when positioned correctly.
Approaching the Tarantula on the lower tier of the town near the sea (in City Folk) will make it walk away from the player, which may direct it to water, where it will fall in and disappear.
When the Tarantula attacks a player, a distinct bite sound can be heard, followed by the player spinning around and falling to the floor. Once bitten, the screen turns black and the player re-appears collapsed outside their house. Nothing will be lost.
Contrary to popular belief, neither the Tarantula nor the Scorpion induce a state of "brain damage" in which the player obtains less money from Tom Nook when selling and the villagers are less friendly to the player.
Donating to the museum
In Wild World
''Hoo my! It's simply amazing that you were able to catch one of these monsters... Not only is it poisonous, it's as hairy as can be... Blech! Hairy and toxic... Is there any combination more vile?"
In City Folk
"Hoo, such foul fuzziness! And have you seen how fast they move? It's enough to make an owl faint. They're quite docile beasts, and it's documented that they rarely attack people... But when I look at them up close like this, I start to wonder if the experts might be wrong, eh wot?!"
It can be found in the first enclosure on the middle terrace, which holds the Scorpion, Centipede, Flea, and Fly, to name a few.
The Scorpion and Tarantula can be seen battling with each other when both have been donated. The Scorpion can be seen shaking its stinger at the Tarantula, which makes a rattling noise. The Tarantula can be heard making a hissing-type noise, which might be associated with the insect's defense mechanism of scratching hairs at enemies. They will circle each other, and eventually both jump into the air and collide, then begin their battle again. If the Scorpion is absent, the Tarantula will watch the player.
In New Leaf
Rather than a small talk by Blathers, information is provided on the Tarantula's enclosure.
"Tarantulas are large arachnids that live in warm areas. They're sometimes kept as pets. They have sharp fangs, and while it is painful if you're bitten by one, they aren't deadly to humans. What's scarier is the hair they kick off of their abdomens to protect themselves. The hair can cause serious itching and rashes wherever it sticks and can be rather difficult to remove."
Before the Scorpion is donated, the Tarantula walks around in its small part of the enclosure. When the player walks near the Tarantula, it will stop in its tracks and stare at the player, turning as the player walks. When the player walks away for long enough, the Tarantula will continue walking. If a scorpion is donated the tarantula and scorpion will jump in the air and slam into each other.
It is unknown what type of tarantula appears in the Animal Crossing games. There are different types of tarantula: ground hunters, tree hunters, as well as poisonous and nonpoisonous ones. Although a tarantula has eyes, its keenest sense is touch. It feels vibrations in the ground and determines the location of its prey through them. They are exothermic, but under a thermal image, the abdomen appears the brighter than the rest of its body (indicating warmth).
The tarantula from the Animal Crossing series resembles the Mexican redknee tarantula (Brachypelma smithi). These terrestrial tarantulas of the west side of Sierra Madre Occidental and Sierra Madre del Sur are popular among enthusiasts. The females can live to be 30 years while the males lead a much shorter 5 years or so. The male has a comparable size to the female, but has a smaller body with longer legs. The tarantula must undergo occasional molting to grow. The Mexican redknee tarantula is docile, unlike the tarantula in Animal Crossing, and it is only slightly venomous.