Tattered Bee Wing

It exists to become Bee Wings and nothing else. If you are not building those, it is loose change. If you are, do not sell a partial set off, because the finished wings are worth more than their parts.

Moss Hornets only live in the Underground Jungle, and on current versions the wing will not drop at all until you have taken down at least one mechanical boss, so an early trip is wasted effort. When you do go, cut a wide flat corridor through the mud and let them come to you rather than chasing them around. Each hornet splits when it dies, so a single spawn is more than one kill.

Bee Wings are middling by the time you can build them, and they arrive in the same window as several other flight options. If you already have wings, skip the grind entirely.