とんぼ

How it works

が (subject) points out とんぼ (dragonfly) as the subject — が (subject) is used here to report something newly noticed, rather than は (topic) which sets up a topic. The verb is 飛んでる(とんでる) (is flying), the contracted casual progressive of 飛ぶ(とぶ) (to fly) (full form 飛んでいる(とんでいる) (is flying)), describing an action happening right now: "A dragonfly is flying."