mayfly
蝣 refers specifically to the mayfly, a short-lived insect.
蝣 combines 虫 (insect) with 斿, which likely contributes the sound ユウ. The character was created to name the mayfly.
The insect radical 虫 beside 斿, which looks like a child 子 holding a flag 方, suggests a delicate, short-lived insect fluttering like a flag in the breeze: the mayfly.
For ユウ, imagine a mayfly drifting on the wind saying 'you' to the world: you -> ユウ, and the mayfly's brief life is a greeting to the day.
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