Bt's are not species specific, but order specific.  They kill larval stages of the order Lepidoptera, which are the insects that undergo egg-larva-pupa-moth/butterfly.  Honeybees are in the order Hymenoptera and are not affected, neither are houseflies which are in the order Diptera, etc.

The Bacillus thuringiensis toxic causes a gastroenteritis in the larval stage which stops feeding.  Most insects that feed on plants in the larval stage are from the order lepidoptera.  Common examples include the corn earworm, bollworm, european corn borer, tobacco budworm, hornworm, etc.