From doodle + bug.

doodlebug (plural doodlebugs)

1. (informal, British) The V-1 flying bomb.
   • 2009, Robert McCrum, The masterpiece that killed George Orwell:

     Soon after Richard was adopted, Orwell's flat was wrecked by a doodlebug.

2. (historical, "doodlebug tractor") An automobile converted into a cheap tractor for a small farm during the Second World War.
3. (entomology) An antlion larva (Myrmeleontidae).
4. (entomology, UK) A cockchafer (genus Melolontha).
5. (entomology, regional) A woodlouse.
6. (informal) A term of endearment.
7. (informal) A slackard or time-waster.
8. (informal) An idiot.
9. (informal) Someone who draws constantly.
10. (informal) A divining rod or similarly intended device.
11. (obsolete) Individual self-propelled train cars.