Day fly and Mayfly

Mayfly and day fly are semantically related. In some cases you can use "Mayfly" instead a noun phrase "Day fly".

Mayfly noun - Slender insect with delicate membranous wings having an aquatic larval stage and terrestrial adult stage usually lasting less than two days.

Day fly and mayfly are semantically related. Sometimes you can replace phrase "Day fly" with "Mayfly", this terms are similar.