Mayflies
Mayflies, also called "upwing flies" are rather delicate-looking insects in the order Ephemeroptera. The early life stages live as nymphs in freshwater and the insects are associated with rivers, canals, lakes and ponds. The name of the order is a reference to the ephemeral (short) life span of the adult insects, often no more than a day. Mayflies are very primitive winged insects, related to the dragonflies and damselflies, with which they share the inability to fold their wings flat over their backs.
The order is unique, in that they are the only insects to have a winged pre-adult stage, called the sub-imago, or "dun" by fly-fishermen. Adult mayflies have two pairs of membranous wings that are held upright when the insect is at rest. The end of the abdomen bears two long cerci often with a central filament. Adult mayflies are 3-25mm long, excluding the tails. Some male mayflies have a pair of bizarre upward-facing "turban-eyes" between the normal compound eyes on their head, thought to be UV-sensitive organs used to detect females flying above them.
Cloeon dipterum nymph with developing wings Cloeon dipterum sub-imago
Mayflies mate on the wing, with the males dying shortly afterwards. The females return to a suitable water body and deposit eggs in the water. In some species, the eggs overwinter before hatching, while in others the eggs hatch after a few weeks and it is the nymphs that overwinter.
Role of mayflies in gardens
Mayfly nymphs are eaten by a wide range of fish and other animals, so are an important part of aquatic food chains. Adult mayflies of some of the common species emerge from the water in huge numbers within a few days of each other. Their mating flights provide rich feeding opportunities for swifts, swallows, house martins and bats.
Other sources of information
Websites
Website of the Riverfly Partnership
Website of the Freshwater Biology Association
Website of the Freshwater Habitats Trust
First Nature page on mayflies
Books
Bauernfeind, E. & Soldan, T. (2012) Mayflies of Europe. Apollo Books
Dobson,M. Pawley,S. Fletcher,M. & Powell, A. (2012) Guide to Freshwater Invertebrates Published by Freshwater Biological Association
Elliott, J. M. & Humpesch, U. H. (1983) A key to the adults of the British Ephemeroptera. Freshwater Biology Association
Elliott, J. M. & Humpesch, U. H. (2012) Mayfly larvae (Ephemeroptera) of Britain and Ireland. Freshwater Biology Association
Harker, J. & Rodford, J. (1990) Naturalists Handbooks 13 Mayflies. Richmond Publishing
Macadam, C. & Bennett, C. (2010) A pictorial guide to British Ephemeroptera. A Field Studies Council AIDGAP key, Preston Montford, Shrewsbury
Page text drafted by Andrew Halstead, reviewed by Andrew Salisbury, compiled by Steve Head
Adult mayflies. Left: pond olive Cloeon dipterum. Right: drake mackerel Ephemera vulgata
Biology
Mayflies have aquatic nymphal stages. Depending on the species, they live in the mud and stones at the bottom of ponds and other waterbodies, or they cling to the foliage of water plants, or they are free-swimming. The nymphs resemble the adult insects but lack wings, and have paired gills along he abdomen. They have three tails on the rear end of the abdomen, even in the species where the adult insects have the tails reduced to two. The nymphs mostly feed on algae, often using filtering cells and particles from the water. Some mayflies have predatory nymphs. Adult mayflies do not feed during their short lives.
Life cycle
The time taken for mayfly nymphs to complete their development varies from a few months to two years, depending on species. When the insect has completed its nymphal stages, it swims to the surface and a winged pre-adult form emerges from the final nymphal instar. This flies a short distance before settling and then the winged adult emerges from the pre-adult stage. Mayflies are unique in the insect world in having this winged pre-adult stage. The pre-adult stage is known to fly-anglers as ‘duns’ and the more brightly coloured adults as ‘spinners’.
Species in Britain and Ireland
There are approximately 50 species in Britain and Ireland. Most are associated with large lakes or rivers and streams but some will breed in garden ponds. The most common species in garden ponds is the aptly named pond olive, Cloeon dipterum. Ephemera vulgata is a large mayfly often seen in large mating displays. Mayflies are not confined to the month of May; adults of various species occur from spring to autumn, although the majority are on the wing during May-August.
"Turban-eyes" on the head of a male Cloeon dipterum
.jpg "Mayfly Cloeon dipterum sub-imago")
Mayflies
Mayflies, also called "upwing flies" are rather delicate-looking insects in the order Ephemeroptera. The early life stages live as nymphs in freshwater and the insects are associated with rivers, canals, lakes and ponds. The name of the order is a reference to the ephemeral (short) life span of the adult insects, often no more than a day. Mayflies are very primitive winged insects, related to the dragonflies and damselflies, with which they share the inability to fold their wings flat over their backs.
The order is unique, in that they are the only insects to have a winged pre-adult stage, called the sub-imago, or "dun" by fly-fishermen. Adult mayflies have two pairs of membranous wings that are held upright when the insect is at rest. The end of the abdomen bears two long cerci often with a central filament. Adult mayflies are 3-25mm long, excluding the tails. Some male mayflies have a pair of bizarre upward-facing "turban-eyes" between the normal compound eyes on their head, thought to be UV-sensitive organs used to detect females flying above them.
"Turban-eyes" on the head of a male Cloeon dipterum
Species in Britain and Ireland
There are approximately 50 species in Britain and Ireland. Most are associated with large lakes or rivers and streams but some will breed in garden ponds. The most common species in garden ponds is the aptly named pond olive, Cloeon dipterum. Ephemera vulgata is a large mayfly often seen in large mating displays. Mayflies are not confined to the month of May; adults of various species occur from spring to autumn, although the majority are on the wing during May-August.
Species in Britain and Ireland
There are approximately 50 species in Britain and Ireland. Most are associated with large lakes or rivers and streams but some will breed in garden ponds. The most common species in garden ponds is the aptly named pond olive, Cloeon dipterum. Ephemera vulgata is a large mayfly often seen in large mating displays. Mayflies are not confined to the month of May; adults of various species occur from spring to autumn, although the majority are on the wing during May-August.
Adult mayflies. Left: pond olive Cloeon dipterum. Right: drake mackerel Ephemera vulgata
Biology
Mayflies have aquatic nymphal stages. Depending on the species, they live in the mud and stones at the bottom of ponds and other waterbodies, or they cling to the foliage of water plants, or they are free-swimming. The nymphs resemble the adult insects but lack wings, and have paired gills along he abdomen. They have three tails on the rear end of the abdomen, even in the species where the adult insects have the tails reduced to two. The nymphs mostly feed on algae, often using filtering cells and particles from the water. Some mayflies have predatory nymphs. Adult mayflies do not feed during their short lives.
Life cycle
The time taken for mayfly nymphs to complete their development varies from a few months to two years, depending on species. When the insect has completed its nymphal stages, it swims to the surface and a winged pre-adult form emerges from the final nymphal instar. This flies a short distance before settling and then the winged adult emerges from the pre-adult stage. Mayflies are unique in the insect world in having this winged pre-adult stage. The pre-adult stage is known to fly-anglers as ‘duns’ and the more brightly coloured adults as ‘spinners’.
Cloeon dipterum nymph with developing wings Cloeon dipterum sub-imago
Mayflies mate on the wing, with the males dying shortly afterwards. The females return to a suitable water body and deposit eggs in the water. In some species, the eggs overwinter before hatching, while in others the eggs hatch after a few weeks and it is the nymphs that overwinter.
Role of mayflies in gardens
Mayfly nymphs are eaten by a wide range of fish and other animals, so are an important part of aquatic food chains. Adult mayflies of some of the common species emerge from the water in huge numbers within a few days of each other. Their mating flights provide rich feeding opportunities for swifts, swallows, house martins and bats.
Other sources of information
Websites
Website of the Riverfly Partnership
Website of the Freshwater Biology Association
Website of the Freshwater Habitats Trust
First Nature page on mayflies
Books
Bauernfeind, E. & Soldan, T. (2012) Mayflies of Europe. Apollo Books
Dobson,M. Pawley,S. Fletcher,M. & Powell, A. (2012) Guide to Freshwater Invertebrates Published by Freshwater Biological Association
Elliott, J. M. & Humpesch, U. H. (1983) A key to the adults of the British Ephemeroptera. Freshwater Biology Association
Elliott, J. M. & Humpesch, U. H. (2012) Mayfly larvae (Ephemeroptera) of Britain and Ireland. Freshwater Biology Association
Harker, J. & Rodford, J. (1990) Naturalists Handbooks 13 Mayflies. Richmond Publishing
Macadam, C. & Bennett, C. (2010) A pictorial guide to British Ephemeroptera. A Field Studies Council AIDGAP key, Preston Montford, Shrewsbury
Page text drafted by Andrew Halstead, reviewed by Andrew Salisbury, compiled by Steve Head
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