i mix oatmeal and hi fibre cereals in a large plastic rubbermaid
container which i keep in a kitchen cabinet over stove...for months at
a time, adding to it...i've notices small flying bugs in this cabinet
and was stupidly shocked to find them in the cereal container...HOW
CAN I KEEP A CEREAL MIXTURE FROM GOINING BUGGY?

It's unfortunate, but true, that sometimes insect eggs and/or larvae
may be present in food when you buy it. This seems particularly true
of foods which contain flour.

If you place newly-purchased food in the freezer for 24 hours, and
afterward keep the food in an air-tight container, the food should
remain bug-free.

Yes, indeedy deed dee!  They are called  - translated - "flour worms"
in German (the larvae), and my wife get almost as upset at their
affront to her housewifing as she did when the kids got lice in
school.
If you buy your cereals at a bio store, the bugs are included in the
price (just think of them as more protein), and they love your keeping
them over the stove.

Thanks for the tip about freezing, Pinkfreud.  I'll suggest it after
the next attack.

if you have bugs in the cereal container then you can bet as pink said
there are eggs. If you keep adding a food source the little critters
are happy to reproduce. Dump your container and buy a new one or wash
it with hot hot soapy water (both extremes of hot and cold will kill
insect eggs and larvae, but don't burn your hands off now). Also, dump
out all the food that was in it, it's contaminated and could contain
more eggs. Bonus: write to the cereal manufacturer and they will
likely send you some vouchers for free boxes of their bug coated
snackies to compensate for your troubles.e