Weevils are beetles, not ants, not "bugs".
The following applies to weevils as well as dermestids (museum beetles) and those damned meal-eating moths.
They experience a full metamorphosis. Meaning: egg, larvae (caterpillar), pupa, adult. Often you won't see them until they are adults.
They do not have nests. There may be many of them in one place, but it's either the food source or where they get stuck.
They eat a wide variety of grain-based foods but will eat other things.
They may well be in your processed, sealed food from the store. More often than not, they got into it when it was at the store. Then they breed, breed, breed until you notice them, often not until adulthood.
Freezing typically will kill larvae and adults- but not eggs. Meaning the problem may go away for a while, but will return.
To get rid of them:
* Throw away all packaged and boxed cereals and meals
. Or, eat them. But get rid of them. Make sure you clean up any messes from spilled, opened, or eaten cereals- look in corners, in the holds, etc. Even if the box or package has never been "opened" by you- it may be been discretely opened by "them".
* When you buy packaged foods like this, freeze it 2 days. Put the original packaging into a Ziploc bag and seal it. Name brand Ziploc is best. Then, put it in Tupperware (not cheap
copies). You should be able to remove the factory sealed package from the box, label it with a Sharpie, and fit a whole bunch into Ziploc then Tupperware.
* If you can, make sure the food is dry- when you buy, when you stuff it in the Ziplocs. These bugs prefer moisture. Museum beetles, for example, will nary reproduce when humidity is below 50%