
1) Ephemerid 2) Ephemeropteran 3) Insect with a short lifespan 4) Mayfly 5) Shadfly 
Found on 
https://www.crosswordclues.com/clue/dayfly

1) Mayfly 2) Shadfly 
Found on 
https://www.crosswordclues.com/clue/dayfly

• (n.) A neuropterous insect of the genus Ephemera and related genera, of many species, and inhabiting fresh water in the larval state; the ephemeral fly; -- so called because it commonly lives but one day in the winged or adult state. See Ephemeral fly, under Ephemeral.
Found on 
http://thinkexist.com/dictionary/meaning/dayfly/
Day'fly` (dā'flī`) 
 noun  (Zoology) A neuropterous insect of the genus 
 Ephemera and related genera, of many species, and inhabiting fresh water in the larval state; the ephemeral fly; -- so called because it commonly lives but one day in the winged or adult state. See 
 Ephemer...Found on 
http://www.encyclo.co.uk/webster/D/9

Dayfly is the popular name of those neuropterous insects which belong to the genua Ephemera. They are so called because, though they may exist in the larval and pupal state for several years, in their perfect form they exist only from a few hours to a few days, taking no food, but only propagating their species and then dying.
Found on 
http://www.probertencyclopaedia.com/browse/BD.HTM
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