Dear Nature Lovers,
Greetings from oikos !

Ephemeroptera is one of the interesting order of insects with very short living insect like Mayfly, whose life span is just few hours to a day ! In Central Europe, one species of Mayfly – ‘Giant Mayfly’ hatch in millions on River Tisza, rise in clouds, reproduce and perish within few hours ! This is known as “Tisza Blooming” and is a major tourist attraction. Watch video for the same :

MAYFLY
ORDER : EPHEMEROPTERA
Caenis spp
The order Ephemeroptera (ephemeros = short living) includes only Mayflies. 
Size up to 1 inch long, has got three tail-like appendages. They complete life cycle within and around water body. Adults are very delicate and have very short life span from few minutes to a day. They emerge in thousands at the same time leading to swarms, mate immediately and lay eggs in water. Nymphs are one of the important part of aquatic food chain … they feed on algae and themselves becoming food for other insects or fishes. 
Wings: Adult with two pair of wings. Also the sub-imago, a stage in between adult and nymph, has two pair of wings.
Mouth Parts: Adults do not feed. So they have non-functional mouth parts.
Metamorphosis: Incomplete. Egg – Nymph – Sub-imago – Adult.
Significance to Humans: Their presence in water body indicate clean and pure water without any pollution so they are known to be good bio-indicators.