/ˈmeɪflaɪ/
[noun] A small, delicate flying insect that lives near water and is famous for having an extremely short adult life, sometimes lasting only a single day.
The mayfly's name is almost a cruel joke — adults cannot eat at all, because they have no working mouth.
The mayfly carries its whole biography in its name. The first part, 'may', refers to the month of May, when these insects famously emerge from rivers and lakes in enormous clouds, briefly filling the air before disappearing just as suddenly. The second element, 'fly', is simply the Old English word 'flēoge', meaning a winged insect, which descends from the Proto-Germanic root 'flaugijō', itself connected to the verb 'fleogan', meaning to fly through the air. The compound 'mayfly' appears in English records from around the 1650s, though the creature had been observed and written about long before anyone settled on a single name for it.
Before 'mayfly' became the standard term, English speakers used a wonderful variety of names for this insect. 'Dayfly' was popular and arguably more accurate, since many species live as adults for only a matter of hours. 'Shadfly' was used in parts of North America, where the insects appeared at the same time as shad fish were running upstream. 'Fishfly' was another common regional name, because anglers knew the mayfly well — trout rise eagerly to the surface when mayflies hatch, making the insect central to the art of fly-fishing. Each of these names reflects a different human relationship with the same tiny creature.
The scientific name for the mayfly's order, Ephemeroptera, tells an even older story. It comes from the ancient Greek 'ephemeros', meaning 'lasting only a day', which itself breaks down into 'epi' (upon) and 'hemera' (day). From this Greek root, ancient Greek passed 'ephemeros' into Latin as 'ephemerus', and from there it entered English in the 16th century as 'ephemeral', meaning something that exists for only a very short time. The journey runs: Ancient Greek 'ephemeros' → Latin 'ephemerus' → English 'ephemeral'. The mayfly, in a sense, gave the English language one of its most poetic words for transience.
What makes the mayfly's story genuinely extraordinary is the contrast between its two lives. Before it becomes the winged adult we recognise, the mayfly spends anywhere from one to three years underwater as a nymph, crawling along riverbeds and slowly developing. Then, in a matter of hours, it sheds its skin, rises into the air, mates, lays its eggs on the water's surface, and dies. The adult form has vestigial, non-functional mouthparts — it cannot eat, because it has no need to. Every calorie it uses in its airborne life was stored during its years underwater. It is, in the most literal sense, living entirely on borrowed time.
The mayfly has fascinated philosophers and writers for thousands of years precisely because of this brutal brevity. Aristotle wrote about it in his 'History of Animals', noting its one-day lifespan with a kind of wonder. In later centuries, preachers and poets used the mayfly as a symbol of human mortality — a reminder that even what feels like a long life is, measured against eternity, gone in an instant. The word 'mayfly' thus carries two meanings at once: a precise entomological label and a quiet philosophical warning, all compressed into seven letters.