midge vs gnat

midge and gnat both are nouns.

Word	Noun	Adjective	Verb	Adverb
midge	Yes	No	No	No
gnat	Yes	No	No	No

As nouns, gnat is a hypernym of midge; that is, gnat is a word with a broader meaning than midge:

midge: minute two-winged mosquito-like fly lacking biting mouthparts; appear in dancing swarms especially near water
gnat: any of various small biting flies: midges; biting midges; black flies; sand flies

midge (noun)	gnat (noun)
minute two-winged mosquito-like fly lacking biting mouthparts; appear in dancing swarms especially near water	any of various small biting flies: midges; biting midges; black flies; sand flies
	(British usage) mosquito