The Drake Mackerel Mayfly (Ephemera vulgata) is one of the largest British mayflies. The nymphs of this species are found in the pools and margins of muddy rivers and still-waters, where they dig into the bed and live in a tubular burrow. They use their gills to circulate water through the burrow.

Emergence of the adults typically takes place at dusk or dawn on the surface of the water or sometimes just above the surface on a stick, stone or plant stem. Males swarm throughout the day, and often continue until dusk. Once mated, the female flies upstream and releases a few eggs by dipping the tip of her abdomen into the water at intervals whilst in flight, or by settling on the water surface for short periods.

The Mayfly typically has a two-year life cycle, however some populations may have an annual lifecycle. Adults can be found between May and August.

The Iron blue dun (Baetis muticus) is one of the most well-known mayfly species. The nymphs can be found in the riffle areas of swift running waters, where they live in gravel or sand on the bed of the watercourse. The nymphs are good swimmers and typically swim in short, darting bursts.

Emergence of the adults typically takes place on the surface of the water during daylight hours. The males of this species can be found swarming throughout the day, however swarming stops at the onset of dusk. Once mated, the female flies to the river and lands on a partly submerged stone. She then closes her wings and climbs under the water to lay her eggs.

There are two generations per year – a slow-growing winter generation and a much faster-growing summer generation. This results in a fairly long flight period, and adults are present between April and October.

The March brown (Rhithrogena germanica) is probably the most famous of all British mayflies. It is sacred to anglers across the UK and has been imitated by them to help catch fish for over 500 years.

March brown (Rhithrogena germanica)

Originally the March brown mayfly was confused with the False (or Late) March brown (Ecdyonurus venosus). But, in 1931, the March brown mayfly (Rhithrogena germanica) was officially recorded in Britain. Today it is found in large, clean rivers such as the River Tweed and River Don in Scotland, the River Wye in Wales , the River Liffey in Ireland and the River Coquet in England.

The March brown is quite extraordinary for a mayfly. Most mayflies like to emerge as adults during the warm summer months, however, the March brown emerges right at the end of the winter – from March to early April. Adults emerge from the river around about midday. The larvae drift in the water and then emerge at the surface. As they are emerging they are an easy target for fish and birds so they emerge very quickly – often taking less than 30 seconds to moult and fly off the water.

In common with other mayflies the March brown has two adult life stages. The adult that emerges from the water is called a subimago or ‘dun’. Usually this stage is relatively short, with the subimago resting on bankside vegetation before moulting its skin again and becoming an imago or ‘spinner’. The March brown however has the longest subimago stage of any mayfly. After they leave the water’s surface they immediately fly to the bank and land on the ground they then fly up to a nearby tree. They’ll then rest in the leaves of the tree for anything up to four days before moulting.

Numbers of this species are in decline across Europe. Whilst the March brown can tolerate some pollution it relies on lots of oxygen in the water. As a result it favours faster flowing stretches of water. It’s thought that because this species has to grow rapidly during the winter that it might be more prone to disturbance due to natural or artificial changes to the conditions in the river during this period.

(This post was originally published on the Buglife website.  Visit www.buglife.org.uk to find out more about Buglife’s work)

The olive upright (Rhithrogena semicolorata) is a common and abundant mayfly of swift running waters. Nymphs can be found in the riffle areas of rivers and streams where they are usually found clinging to submerged plants and stones, although they may swim if disturbed.

Emergence of the adults typically takes place at the surface of the water at anytime between dawn and dusk. Males of this species can be found swarming throughout the day. Once mated, the female flies upstream and releases a few eggs by dipping the tip of her abdomen into the water at intervals whilst in flight, or by settling on the water surface for short periods.

There is one generation per year that overwinters as nymphs. As growth rates vary with water temperature, the periods over which adults emerge is variable, but adults have been found between April and September in the British Isles.

Those of you that know me will realise that this is a question my barber has been asking for some time! This post isn’t however so much about the follicularly challenged amongst us but about the identification of larval Needle flies, or to give them their Sunday name – the Leuctridae.

There are six species of Leuctridae known from the British Isles – Euleuctra geniculata; Leuctra nigra; L. fusca; L. inermis; L. hippopus; and L. moselyi. For the beginner the identification of these species is troublesome at best! Hopefully the notes below will help you out.

The Willow fly (Euleuctra geniculata) is relatively easy to separate from the other Leuctridae. When fully grown it is the largest of the Leuctridae, growing to around 10mm. It’s also quite sturdy with a broad head and stout antennae which lead Richard Chadd at the EA to comment that it looks a bit ‘goaty’! The clincher though for this species are the growths on the segments of the antennae closest to the head which, to the naked eye, make them look ‘knobbly’.

A bit 'goaty' - Euleuctra geniculata

Next species to tackle is L. nigra. The Leuctridae are generally drab animals in shades of brown however L. nigra is much brighter, tending towards orangey-yellow and is covered in fine hairs. The best place to see these hairs is on the pronotum (the bit behind the head). One thing to note though is that the Chloroperlidae (of which there are two species in the UK) are also very hairy, however they can be separated by the shape of the wing pads and the arrangement of the segments of the tarsi (or foot). In the Leuctridae the wing pads are long, straight and slender whereas the Chloroperlidae have ‘pac man’ shaped wing pads. The segments of the tarsi in the Leuctridae are arranged (starting closest to the body) in a long-short-long pattern whereas those of the Chloroperlidae are short-short-extra long.

With those two species out of the way we now get to the nub of the problem – L. fusca is separated from the remaining species by having a fringe of long hairs on the rear edge of each tibia. Until quite recently I would have said that the most common species of Leuctridae in the UK was L. inermis as 9 out of 10 specimens I looked at keyed out at this species. However, a discussion with David Pryce about some work he was undertaking on adult stoneflies revealed that L. fusca is by far the more common species (certainly in Scotland). On revisiting a number (lots) of specimens identified as L. inermis I discovered that they did indeed have long hairs on the tibia, however you could hardly call it a fringe! Perhaps the hairs have been rubbed off or perhaps they were never there at all? There’s a bit more work to do here but if your specimen is greater than 5mm and has 6 or more hairs on the rear edge of the tibia I’d consider L. fusca as an option.

True specimens of L. inermis should be fringeless or (just to prove Sod’s law works with stoneflies as well) with several (<6?) long hairs not forming a fringe. They should also have a series of long bristles on their back. There should be at least one pair, sometimes more on each segment apart from the one closest to the thorax. One thing to note though is that in preserved Leuctridae the body sometimes becomes slightly detached from the thorax and rotated so that the ‘back’ of the larva is in fact at the side of the animal, however if the bristles are there you should be able to see them with x20 magnification and some light from below.

The final two species (L. hippopus and L. moselyi) are notoriously difficult to separate. The current key to British stoneflies starts with their relative size at a certain time of year – greater than 5mm between October and May would suggest L. hippopus whereas greater than 5mm between May and September should be L. moselyi. As you can see these time periods overlap so potentially a specimen in May could be either species. Add to this the possibility that climate change has affected the development of these species then it’s possible that these time periods may have shifted by a month or more. The only sure-fire way to separate these is to make sure you have a fully-grown specimen. L. hippopus should have more than twelve bristles on each side of the pronotum (remember – the bit behind the head) whereas L. moselyi will have less than twelve (however look carefully as these bristles are difficult to see!).

So to summarise – the Leuctridae are ‘do-able’ but you need to watch out for some potential elephant traps along the way. The other thing we’ve learned is that a fringe can have as few as 6 hairs – can’t wait to tell my barber!

The Large dark olive (Baetis rhodani) is one of the most common and abundant mayflies of swift running waters.  Nymphs can be found in the riffle areas of rivers and streams, where they swim in short bursts, interspersed with periods of clinging to submerged plants and stones. They are often found in short, swift stretches of otherwise sluggish rivers and streams.

Emergence of the adults typically takes place at the surface of the water during daylight and at dusk.  Males of this species can be found swarming throughout the day. Once mated, the female flies to the river and lands on a partly submerged stone.  She then closes her wings and climbs under the water to lay her eggs.

There are two generations per year – a slow growing winter generation and a much faster summer generation. This results in a long flight period, and adults are present between March and November, although in mild years adults may be flying in every month.

A man turns up at a fancy dress party dressed in a suit and clutching a standby ticket for a British Airways flight to New York.  The host of the party asks “What have you come as?”.  The man replies “I’m a mayfly – I may fly tomorrow or I may not!”.

Oh, sorry ‘humeral’ not ‘humorous’…..  What I really wanted to talk about was mayfly wings.

Mayflies were the first insects to free themselves from the chains of a purely terrestrial life.  Their ability to fly has helped them to persist for over 300 million years.  But how many of us have looked closely at the structure of their wings?

The basic formula for an insect’s wing is a series of longitudinal veins with a varying number of cross veins between them.  The purpose of these veins is to give strength and stability to the wing membrane in flight.  We can think of the wing membrane as a piece of paper.  If you stand a sheet of paper on its edge it will probably fall over.  Similarly if you take an end of the paper in each of your hands and bring your hand together the paper will flex and bend completely.  The veins stop the gross flexing of the wing and also support the wing when at rest.  Looking closely at the wing you’ll see that the membrane is pleated with the longitudinal veins following an alternating concave – convex pattern.  The reason for this is simple.  If you take your piece of paper and fold it as if you’re making a fan- fold one way, then the next with about 2 centimetres for each fold.  Now stand it up along the folds – et voila!  The paper is able to stand upright without support.  Furthermore, if you put weight on the top of the folds it can support that weight easily.

So let’s have a closer look at the veins.  From the front of the wing is the costal area or costal margin.  The first vein encountered here is the costa.  This thick, strong vein is the backbone to the wing – think of it like the mast of a sail.  The costa is complemented by the sub-costa which typically runs parallel it.  At the top of this section is the pterostigma.  This area often contains a number of small cross-veins and can also be shaded or patterned in some way.  In some species, such as the Pond Olive (Cloeon dipterum), the whole of the costal margin is patterned with brown pigment.  In other species, for example Ecdyonurus insignis it is only the pterostigma that is coloured.  The number of veins in the pterostigma can also be used to separate some species, most noticeably the two Cloeon species – C. dipterum and C. simile.

The next area of the wing is the radial sector.  This area is delineated by the branches of the next longitudinal vein – the radius.  In the archetypal Ephemeroptera wing the radius has five branches, number R1 to R5.  R1 runs parallel to the costa and sub-costa, and runs the full length of the wing.  R2 and R4 both branch off close to the base of R1.  These veins then branch again towards the centre of the wing to form R3 and R5.  The branch between R4 and R5 is termed the ‘outer fork’ and is one of the distinctive features of Ephemeroptera wings.

The radial sector occupies half of the area of the wing.  The remaining area, towards the body of the insects is occupied by The median, cubitus and anal veins.  The median vein splits into two separate veins (M1 and M2) close to the base of the wing.  In the Ephemeridae and Potamanthidae M2 arches strongly away from the M1 where it splits.  This feature helps to separate these families from the Leptophlebiidae and Ephemerellidae.

The cubitus follows the median and also splits close to the base of the vein.  The relative distance between Cu1, Cu2 and the first anal vein is important for separating Leptophlebiidae and Ephemerellidae.

The anal veins, which vary in number, are largely incidental.

Between each of the major longitudinal veins there can be a number of other minor veins that are connected to the major veins by cross-veins.  These minor veins also follow the concave – convex pattern and add further stability to the wing structure.

At the edge of the wing, between the major veins some species have intercalary veins.  These veins are typically short and ‘free’ – unattached to other veins.  The most commonly known of these intercalary veins are the paired intercalaries found in Baetis sp., however other species that have intercalaries include: single intercalary veins in the Ephemerellidae, Procloeon, Cloeon and Centroptilum; wavy intercalaries between Cu1 and Cu2 in Siphlonurus spp. and Ameletus inopinatus; and two pairs of long intercalaries between Cu1 and Cu2 in the Heptageniidae.

Cross-veins are an important feature of the wing.  If you take your piece of paper and push either end of it together the folds will concertina together until the whole piece of paper folds flat.  The cross-veins make sure that the folds remain in position and prevents any concertina effect.  They are also useful tools for identification.  For example, in Procloeon bifidum the cross-veins between the Sub-costa, R1 and R2 all line up.  In Ecydyonurus venosus this is taken a step further with many of the cross veins in the Radial sector lining up.  The cross-veins also help to produce the colour and patterning, particularly in the sub-imago.  For example the clear ‘window’ that is found in the mottled wing of the March brown (Rhithrogena germanica) is due to an absence of cross-vein in that area of the wing.  Similarly, the patterning on the wings of the Brook dun (Ecdyonurus torrentis) is due to colouring around the cross-veins.

It would be remiss to leave this discussions of wings and veins without mentioning one of the features that separates Ephemeroptera from the other orders of winged insects.  At the base of the wing, spanning between the costa, sub-costa and radius is a thick, sturdy cross vein called the ‘costal brace’  This feature is unique to the Ephemeroptera and is used in Paleontological studies to recognise early Ephemeroptera in fossils.

If there’s one thing that I get asked more than anything it’s how to separate larvae of the four British Ecdyonurus species.  I’m not surprised though as most keys rely on the shape of the head and the pronotum and while with practice (and enough specimens) you can begin to separate out species using these features it is rather subjective and rather difficult even for the experienced.  There are however some other features that can be used on fully mature larvae.  Of course Ecdyonurus insignis can be quickly separated by the pattern of dark lines on the pale underside of the body.

Ecdyonurus insignis: markings on the underside of the body

It should be noted that the absence of a tuft of filaments on the last gill is not always reliable as occasionally there can be a small tuft alongside the plate-like gill.

To separate the other Ecdyonurus species we must first look at the markings on their tarsi (feet).

Tarsi with one dark band: Ecdyonurus venosus

Tarsi with 2 dark bands: Ecdyonurus dispar or Ecdyonurus torrentis

 

 

 

 

Ecdyonurus dispar and E. torrentis can then be separated by the markings on the underside of the body.

Dark line at front of body segment: Ecdyonurus dispar

Inverse pattern of dots and lines: Ecdyonurus torrentis

 

 

 

 

This will hopefully help you to get to grips with identifying Ecdyonurus larvae – just remember that it only works on mature specimens!

“What’s in a name?  That which we call a rose, by any other name would smell so sweet”.  When Shakespeare wrote these words in Romeo and Juliet he was referring to the fact that a name is an artificial, meaningless label.  Shakespeare may have known a lot about words and how to use them, but he is not known for his fly-fishing abilities.

So what is in the name ‘Mayfly’.  This is one of those rare occasions when etymology, the study of words, meets entomology, the study of insects.

Anglers of course hold great claim to the name ‘Mayfly’ to describe the Green drake (Ephemera danica).  It’s thought that this claim dates to a translation of a Dutch work on Palingenia longicauda by Jo. Swammerdam in 1675.  Dr. Edward Tyson wrote in his translation of 1681 that “I doubt not but upon a strict inquiry we may meet with Ephemerons here in England…Our Mayfly may well deserve to be examined.”  Many other works since have extolled the virtues of Mayfly hatches on the chalkstreams.  ‘Duffer’s fortnight’ is an institution not to be missed.

So if the Mayfly is Ephemera danica (or E. vulgata or E. lineata) then what should we call the rest of the Ephemroptera?  In recent years the term ‘upwing flies’ has grown in use, however I feel that this is a cumbersome and ugly term – certainly not befitting such wonderful insects as the Ephemeroptera.  A far better name I believe is ‘dayflies’.

The term ‘dayflies’ is not without precedence.  In many European countries the literal translation of the common name for the Ephemeroptera is ‘day-flying’ or ‘day fly’.  For example, in Germany they are Eintagsfliegen.  In Denmark they are Døgnfluer.  Indeed, even in the UK they have been called Dayflies in the past.  In 1950 the Royal Entomological Society published ‘Ephemeroptera: Mayflies or Dayflies’, written by Douglas Kimmins.  Perhaps this was an attempt by Kimmins to clarify the distinction between the Mayfly of the angler and the entomologist.

The use of ‘dayflies’ is as justified as ‘upwing flies’.  The adult lives of most Ephemeroptera rarely last more than 24 hours, and whilst some species are active at night, they are more usually associated with their hatches and swarming during the day.

So will you join me in my campaign to replace the awkward ‘upwing flies’ with the more elegant ‘dayflies’ as the name for Ephemeroptera species other than Ephemera?

This article was first published on the Biofresh Blog

The mayfly’s lifecycle is one of the most fascinating and fleeting stories in the natural world.  One of the many charactersistics that makes mayflies the unique insects they are is the potential for two different winged adult forms in their life cycle. The nymph emerges from the water as a dull-coloured sub-imago (or dun) that seeks shelter in bankside vegetation and trees. After a period of a couple of hours or more, the sub-imago once again sheds its skin to transform into the brightly coloured imago (or spinner).  It is not clear why mayflies have retained this unique step in their lifecycle, however it is thought that they may not be able to achieve the change from nymph to sexually mature adult in one step.

A mayfly’s life cycle starts with the males forming a swarm above the water and the females flying into the swarm to mate.  The male grabs a passing female with its elongated front legs and the pair mate in flight. After copulation, the male releases the female, which then descends to the surface of the water where she lays her eggs. Once mated she will fall, spent, onto the water surface to lie motionless, with her wings flat on the surface, where fish pick them off at their leisure. The male fly rarely returns to the water but instead he goes off to die on the nearby land.

The eggs fall to the bottom of the water where they stick to plants and stones. Flies of the Mayfly family Baetidae pull themselves under the water to attach their eggs directly to the bed before being drowned by the current. The nymphs take anything between a few days to a number of weeks to hatch depending on water conditions and the species, and the resultant nymphs will spend various lengths of time, up to two years, foraging on the bottom before emerging as an adult fly.

When it is time to emerge, the nymphs make their way to the surface where they pull themselves free of their nymphal shuck and emerge as a sub-imago. While they rest here to dry their newly exposed wings, they are at their most vulnerable to attack from fish.

Some species exhibit great synchronicity in their hatching.  The North American species Hexagenia limbata hatches in huge numbers from the Mississippi every year.  The total number of mayflies in this hatch are estimated to be around 18 trillion – more than 3,000 times the number of people on earth.  The newly emerged insects are attracted to lights in riverside towns and villages and the local authorities deploy snow clearing vehicle to remove their rotting corpses.  Ironically, what is seen as a nuisance in America is seen as a gift in Africa.  Locals around Lake Victoria gather adults of the mayfly Povilla adusta together with Chironomid midges to make a type of patty called ‘Kungu’.  This protein rich food stuff is an important part of their diet.