The Blue Beetle was a costumed hero first appearing in Mystery Men Comics #1 (August 1939). Dan Garret (just one "t" to begin with) was a rookie policeman whose father had been killed by a criminal. Over the years, the Blue Beetle underwent a number of changes and eventually the name went to Taxes teenager Jaime Reyes who became the crime fighter via a magic scarab. Evidently the Blue Beetle is still going strong.
The radio show, however, was not strong enough to survive its short run from May to September, 1940. Taking the lead as the original Blue Beetle for the first thirteen shows was Frank Lovejoy, after which he was replaced by an unknown actor.
Here's the first episode, Opium Gang: