plant bug vs mirid bug

plant bug and mirid bug both are nouns.

Word	Noun	Adjective	Verb	Adverb
plant bug	Yes	No	No	No
mirid bug	Yes	No	No	No

As nouns, mirid bug is a hyponym of plant bug; that is, mirid bug is a word with a more specific, narrower meaning than plant bug:

Other hyponyms of plant bug include capsid, mirid, lace bug.

plant bug (noun)	mirid bug (noun)
small bright-colored insect that feeds on plant juices	a variety of leaf bug