Swallowtail butterflies have particularly large wings for their body size, and flap them relatively infrequently.

燕尾蝶有着相对于它们的身体而言十分巨大的翅膀，并且扇动的频率少见地慢。

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They've never sprinted headlong into a flock of seagulls to watch them flap and scatter.

他们也不曾猛冲入海鸥群中，看着它们振翅四散。

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Because their two sets of wings effectively flap as one, that in theory gives them little control over the aerodynamic forces on their body.

因为它们的两副翅膀叠在一起，在空气动力学的理论中，这意味着它们对自己身体缺乏控制力。

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Just as he starts removing the diagrams from the envelope in the back flap, he changes his mind and stuffs them back into the envelope.

BBC: The sex manual for ultra-Orthodox Jews

Remember the flap over Olympics medals and the cash prizes that come with them?

FORBES: All Prizes Trigger Taxes (And You Can't Pay IRS In Doughnuts)