1) Arthropod family 2) Family ephemeridae 3) Mayflies 
Ephemeridae is a family of mayflies with about 150 described species found throughout the world except Australia and Oceania. These are generally quite large mayflies (up to 35 mm) with either two or three very long tails. Many species have distinctively patterned wings. Ephemerids breed in a wide range of waters, usually requiring a layer of silt...
[n] - mayflies
family Ephemeridae noun mayflies