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Order Ephemeroptera - Mayflies
(Ephemero-ptera, from Greek ephemeros = living a day, pteron = wing) |
Class: Insecta Order: Ephemeroptera |
Examples: |
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Soft-bodied insects with large eyes, very short antennae
and atrophied mouthparts. Wings membranous with many veins, hind pair small
or even absent. Wings held vertically upwards when at rest. Front legs of
males are often very long and used to hold the female during mating. Abdomen
terminated by a pair of very long, many-segmented, thread-like cerci,
sometimes with a third median tail filament. Mayflies are unique among
insects in moulting after reaching the adult winged state (the first
winged stage is called the subimago and has a dull appearance
due to a covering of very fine hairs - this outer skin is shed within
a few hours of emergence, revealing the mature adult, recognisable by
its shiny appearance and full colouration). Simple metamorphosis,
with over 20 nymphal moults before the adult stage in some species. The
nymphs are aquatic, with three tail filaments and several pairs of
plate-like tracheal gills that grow out from the sides of the abdomen.
These gills are used for breathing, by absorbing oxygen directly from
the water. About 2,100 species have been described, of which 51 occur in
the British Isles. |
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Ephemera danica (with nymph of Cloeon sp.
illustrated) |
Description. Adults of
Ephemera danica, which are about 15-20 mm long excluding the
'tails', have a brown thorax and pale yellowish-white abdomen with
darker brown markings on most segments. The fore-wings have a
conspicuous dark streak across the middle and smaller dark patches
near the base, which together with the distinctive abominal colouring
make this species one of the most easily recognised mayflies. Nymphs
mainly brown, up to 30 mm long.
Biology. Adult mayflies are
usually found close to rivers, streams and other bodies of freshwater.
The adults do not feed and generally live for less than a day. During
this brief existence they mate and lay eggs. Most species simply drop
their eggs into the water, but some may descend into the water to lay
their eggs on submerged plants. The nymphs of Ephemera live and
burrow in gravel, sandy or muddy areas of rivers and lakes. Other species
live under stones and amongst aquatic weeds in fast and slow moving rivers
and streams, or in some cases in ponds and lakes. The nymphs of Cloeon
(illustrated) are found mainly in still water, or sometimes in in very
slow rivers, clinging to stones and vegetation. Mayfly nymphs are mainly
herbivorous, feeding on plant debris and algae. Nymphal development may
take up to two years, but most mayflies complete their life cycle in one
year.
Distribution. Both
Ephemera and Cloeon spp. are widespread throughout
northern and central Europe, including the British Isles.
Photos: (Ephemera adult) C. Macadam ©
; (Cloeon nymph) V.J. Stanek © |

Adult (Ephemera danica)

Nymph (Cloeon sp.) |

(classification of insects) |

(identification key to insect orders) |
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