The scorpion and tarantula in Animal Crossing are rare bugs that are mainly docile, unless you approach them with your net out. When you have your net out they will look at you and freeze in place. If you try to catch one and miss it will chase you and try to sting or bite you. When the player gets stung or bit, they pass out and then awaken at the front of their house. If, while chasing you, the scorpion or tarantula falls in the water, it will die, and you can’t catch it. You can only catch it if you catch it on the first try.
Honestly I'm surprised that something hostile would be put in this game because it's not a kind of game with hostile things in it, besides the scorpion, tarantula, or bees. If you donate a scorpion and a tarantula to the museum then you may see them fighting. They would repeatedly circle each other, jumping at one another and colliding in mid air.
