Why cats bite when you touch their bellies:
1. It's a normal conditioned reflex in cats. If someone pets a cat's belly while it's sleeping, the cat will develop a conditioned reflex and immediately bite the owner's hand.
2. A cat's belly is its most sensitive area. If a cat feels unsafe in its environment, touching its sensitive area will trigger an attack.
3. Cats like to bite their owners. If the owner often teases the cat with their hand, the cat will like to bite your hand. So when you put your hand on its belly, it will think you are playing with it.
4. If you pet a cat and it makes it feel uncomfortable, it will bite you when you pet it. 
Signs that a cat doesn't trust its owner:
1. It strongly resists being touched by its owner. If the owner reaches out to touch it, it will run away, or its fur will stand on end, it will act aggressively, and it will open its mouth and hiss.
2. Disobeying the master's orders and doing things their own way.
3. Never licks its owner, never actively seeks to be petted, and never acts affectionately.
4. Being very alert when sleeping at home, waking up immediately at the slightest noise, or hiding to sleep are all signs of insecurity and distrust.
5. They are possessive of your food; they are very alert when eating.
6. They often have airplane ears, or their tails droop or are tucked between their legs.
