WordNet records no synonym and no antonym for streamer fly. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
an artificial fly that has wings extending back beyond the crook of the fishhook
Synonyms, antonyms and the broader and narrower relations for streamer fly come from Princeton University’s WordNet. Full sources and licences.