Flies are a pest unto humanity and nature alike, as they contribute nothing, but are not necessarily poisonous, but are bothersome or troublesome.

• 苍蝇是一种既对人类也对自然界而言是害虫的东西，因为它们不会做出任何贡献，虽然不一定有毒，但却是令人烦恼和讨厌的。