Mayflies or shadflies are insects belonging to the order Ephemeroptera ( from the Greek εφημερος , ephemeros = `` short-lived '' ( literally `` lasting a day '' `` daily '' or `` day-long '' ) , πτερον , pteron = `` wing '' , referring to the brief lifespan of adults ) .
Mayflies are insects which belong to the Order Ephemeroptera .