Ephemeroptera, commonly known as mayflies, are short-lived winged insects with aquatic nymph stages that play a crucial role in freshwater ecosystems as indicators of ecological health. Adult mayflies, which live for only a day or two, engage in swarming flights for mating, with females typically laying eggs on or near water surfaces. They serve as an essential food source for various fish and other animals, making them significant both ecologically and economically.

1. Ephemeroptera

2. • Members of this order include: mayflies
(sometimes called fishflies).
• Etymology:
• Ephemeroptera comes from the Greek
ephemera, which means ephemeral or short-
lived, and ptera, which means wings.
• Ephemeroptera, therefore, means a winged
insect with a short life - the typical adult mayfly
lives only a day or so.

3. • Mayflies are small to medium-sized, elongate, very soft-
bodied insects with two or three long, threadlike tails.
• They are common near ponds and streams.
• The adults have membranous wings with numerous veins.
• The front wings are usually large and triangular, and the
hind wings are small and rounded.
• Some species have the front wings more elongate and the
hind wings very small or absent.
• The wings at rest are held together above the body.
• The antennae are small, bristle like, and inconspicuous.
• The immature stages are aquatic, and the metamorphosis
is simple.

4. • May fly nymphs (Naiads - any of a class of nymphs
found in rivers and springs) are found in a variety of
aquatic habitats.
• Some are streamlined in form and very active,
• And others are burrowing in habit.
• They can usually be recognized by the leaf like or
plumose gills along the sides of the abdomen and the
three (rarely two) longtails.
• Stonefly nymphs are similar, but have only two tails
(the cerci), and the gills are on the thorax (only rarely
on the abdomen) and are not leaf like.
• Mayfly nymphs feed chiefly on algae and detritus.
• Many are most active at night.

6. Naiad of dragon fly
Naiad of May fly
Naiad of damsel fly
Naiad of stone fly

7. • Larval life approximately 3-6 months
• Moults many times (12-30)
• When ready to transform to the winged stage, a
mayfly nymph rises to the surface of the water and
molts and a winged form flies a short distance to
the shore where it usually alights on vegetation.
• This stage, which is not the adult, is called a
subimago.
• It molts once more, usually the next day, to
become the adult.
• The subimago is dull in appearance and somewhat
pubescent.

8. • There are hairs along the wing margin and on the
caudal filaments (these areas are nearly always bare in
the adults), and the genitalia are not fully developed.
• The adult is usually smooth and shining; it has longer
legs and tails than the subimago; and its genitalia are
fully developed.
• The mayflies are the only insects that molt again after
the wings become functional.
• The nymphs may require a year or two to develop, but
the adults (which have vestigial mouthparts and do
not feed) seldom live more than a day or two.

9. • Adult mayflies often engage in rather spectacular
swarming flights during which mating takes
place.
• The individuals in the swarm are usually all
males.
• Sooner or later females enter the swarm, and a
male will seize a female and fly away with her.
• Mating occurs in flight, and oviposition generally
occurs very shortly thereafter (within minutes or,
at most, a few hours).

10. • The eggs are laid on the surface of the water or are attached
to objects in the water.
• Eggs hatch in a few days or in 3-9 months depending on the
water temperature
• In cases where the eggs are laid on the surface of the water,
they may simply be washed off the end of the abdomen a few
at a time, or they may all be laid in one clump.
• Each species has characteristic egg-Iaying habits.
• A few species are ovoviviparous.

11. • Feed on detritus, algae, macrophytes
• Few carnivores
• Usually change diet as size of insect increase
• The chief economic importance of mayflies
lies in their value as food for fish.
• Both adults and nymphs are an important
food of many freshwater fish, and many
artificial flies used by fishermen are modelled
after these insects.

12. • Mayflies also serve as food for many other
animals, including birds, amphibians, spiders, and
many predaceous insects.
• Most species of mayflies in the nymphal stage
are restricted to particular types of habitats.
• Hence, the mayfly fauna of an aquatic habitat
may serve as an indicator of the ecological
characteristics (including the degree of pollution)
of that habitat.

13. • The head.
• The compound eyes often differ in the two sexes, being
generally larger and closer together in the male, and
smaller and farther apart in the female.
• In most of the smaller species, such as the Caenidae,
the eyes are small and widely separated in both sexes.
• The eyes of the male are often larger or have upper
facets that are a different color from the other facets.
• The eyes of the female are usually uniform in color and
facet size.
• In the Baetidae and some Leptophlebiidae, the upper
facets are more or less on stalks (such eyes are
described asturbinate).

14. Eyes of male mayflies – close together
Eyes of female
mayflies – not close
together