day-fly
ETYM New Lat., from Greek ephemeros a day fly.
Something transitory; lasting a day.
Slender insect with delicate membranous wings having an aquatic larval stage and terrestrial adult stage usually lasting less than two days; SYN. dayfly, shadfly.
Any insect of the order Ephemerida (Greek ephemeros “lasting for a day”, an allusion to the very brief life of the adult). The larval stage, which can last a year or more, is passed in water, the adult form developing gradually from the nymph through successive molts. The adult has transparent, net-veined wings.