"The birds and the bees" (sometimes expanded to "the birds, the bees and the butterflies" or "the birds, the bees, the flowers, and the trees") is an idiomatic expression which refers to courtship and sex, and is usually used in reference to teaching someone, often a young child, about sex and pregnancy. The phrase is evocative of the metaphors and euphemisms often used to avoid speaking openly and technically about the subject.

According to tradition, the birds and the bees is a metaphorical story sometimes told to children in an attempt to explain the mechanics and consequence of sexual intercourse. According to that story the birds are like men and the bees like women: Birds are free to fly wherever they like, but bees are enslaved to a single queen their entire life and their whole life is dedicated to keeping her alive. Bees pollinate flowers, birds spread the seed, men impregnate eggs, women give birth. Sex is key for survival of both.

Word sleuths William and Mary Morris[1] hint that it may have been inspired by words like these from the poet Samuel Coleridge (1825): 'All nature seems at work ... The bees are stirring--birds are on the wing ... and I the while, the sole unbusy thing, not honey make, nor pair, nor build, nor sing.'"[2]

Several sources give credit to Cole Porter for coining the phrase.[3] One of the legendary musician's more famous songs was "Let's Do It, Let's Fall in Love." The 1928 standard contains the lyrics:[4]

And that's why birds do it, bees do it
Even educated fleas do it
Let's do it, let's fall in love

Another use of this phrase comes from the work of John Burroughs, a naturalist who lived and worked in the Catskills Mountains. He wrote a small pamphlet called "Birds and Bees: Essays"[5] in which he explained the workings of nature in a way that children could understand. However, birds and bees are dealt with in separate sections; nowhere are they mentioned together.