fruit fly vs two-winged insects

fruit fly and two-winged insects both are nouns.

Word	Noun	Adjective	Verb	Adverb
fruit fly	Yes	No	No	No
two-winged insects	Yes	No	No	No

As nouns, two-winged insects is a hypernym of fruit fly; that is, two-winged insects is a word with a broader meaning than fruit fly:

fruit fly: any of numerous small insects whose larvae feed on fruits
two-winged insects: insects having usually a single pair of functional wings (anterior pair) with the posterior pair reduced to small knobbed structures and mouth parts adapted for sucking or lapping or piercing

Other hypernyms of fruit fly include dipteran, dipteron, dipterous insect.

fruit fly (noun)	two-winged insects (noun)
any of numerous small insects whose larvae feed on fruits	insects having usually a single pair of functional wings (anterior pair) with the posterior pair reduced to small knobbed structures and mouth parts adapted for sucking or lapping or piercing