Answer:

bug

Answer	Crossword Clue
BUG	Glitch
BUG	Listening device
BUG	Annoy

BUG	Pester
BUG	Program problem
BUG	Eavesdropper's aid
BUG	Surveillance device
BUG	Plant microphones
BUG	Windshield casualty
BUG	Problem evident during runtime
BUG	Programmer's problem

BUG	Beta tester's find, maybe
BUG	Irritate
BUG	Creepy-crawly
BUG	Eat at
BUG	Wire-tapping device
BUG	Good listener?
BUG	... zapper (back yard killer)
BUG	Cockroach, for one

BUG	Flu or fly
BUG	Cockroach or cicada
BUG	Bother
BUG	Wiretap
BUG	Hidden mike
BUG	There one "planted" in each theme entry
BUG	Computer program glitch
BUG	Spy's favorite plant?

BUG	Volkswagen Type 1, familiarly
BUG	Software issue
BUG	Windows imperfection
BUG	Spying device
BUG	Annoy, so to speak
BUG	Unseen mic, maybe
BUG	Two rivers of this name crossed by German armies, 1939-1941.
BUG	Polish river.

BUG	Insect.
BUG	Flaw in an invention: Colloq.
BUG	A defect, as in a machine: Slang.
BUG	Mantis.
BUG	Spider.