I read that "a bag of wheatberries we purchased in the Midwest six months ago. You can see where the weevils chewed through the plastic bag. " under the picture(from a blogger) showing the holes and weevils.
Do grain weevils or rice weevils bite wood or human? I still found one or two on the paint wall after I threw away the package of the rice weeks ago.
My floor is formed by wooden strips. If they hide and bite there, it'd be troublesome.
What would they eat without grain to keep alive?

None of the grain weevils have the mouthparts to "bite" people. The ones you found are looking for grain to lay eggs in. A strong disinfectant/detergent in your storage area will help get rid of the survivors.

Michigan State University (http://www.pestid.msu.edu/insects-and-arthropods/grain-weevils/)

Thanks for your advice. I know they have a spike thing on their head. Today I found out why the weevils survive in my home after there is no rice there for weeks. I clean up the cupboard and found a box of black-eye beans with lots of weevils in there with white powder. Several months ago I wanted to heat the beans and make a hand warmer with it. But I forgot the whole thing.
Next time if I heat the bean, what temperature to kill the weevil eggs?
Why they like the painted wall? It's like nutritious carbohydrate food? Thank you.

By the time you heat the beans enough to kill all the weevil eggs, they will be paste. It would be better and MUCH more effective to get rid of the infested beans. What color is the painted wall? Does it resemble the color of grain?

Not the infested bean.s I mean if I buy new beans to make hand warmer as I'd thought of heat it before putting them into the cloth bag. I think the degree of baking omelette is enough. Haha. Yes, the painted wall color is like pale black-eye bean skin. I wonder if the kidney bean weevils would like kidney color wood floor hahaha.

Your best bet is to completely empty the storage area, throw away anything showing signs of infestation, and cleaning the area with a strong disinfectant. Personally, I find ammonia cleaners do a good job the first time so there's no need for a second.