They swim around in schools or pods and they are related to whales.
My first is twice in apple but not once in tart.
My second is in liver but not in heart.
My third is in giant and also in ghost.
Whole I'm best when I am toast.
Both cockroaches and illegal drug laboratories or syndicates do fear this.See answer
What becomes too young the longer it exists?See answer
Select a pack of riddles and try to solve it in an interesting way.
This riddle appears in the following downloadable PDF files: