Why were there worms in my cereal?!?!?

i was eating some raisin bran, and i guess its a few to several months old but it didnt taste stale so i ate it anyway and on my 2nd bowl i found tiny dried WORMS in it. yeah so ive been eating them?!?! my mom said she didnt know they could be in cereal but she said she found them in dry noodles before. anyone know WHAT ARE THEY AND WHAT DO THEY DO TO YOU?! AND HOW DO THEY GET THEREEE?!