moths perform as marriage-priests

An example of metaphor in a scientist's writing

"The forty-nine lower flowers of a spike from Folkestone (sent me by Sir Charles Lyell) actually produced forty-eight fine seed-capsules; and of the sixty-nine lower flowers in three other spikes, seven alone had failed to produce capsules. These facts show conclusively how well moths had performed their office of marriage-priests."

Charles Darwin (writing about fertilisation of Orchis pyramidalis)

Darwin, C. (1862). On the Various Contrivances by which British and Foreign Orchids are Fertilised by Insects, and on the Good Effects of Intercrossing. John Murray.