Saturday 27^th May 2023 was a beautiful sunny morning and although cloud built later conditions remained bright and pleasant with good breaks in the cloud and warm spring sunshine. This weather allows for comfortable walking and great close views of butterflies and day-flying moths which can be unapproachable in hot weather and impossible to find when it is cold. In short, conditions were perfect for Butterfly Conservation Ireland’s walk on Lullybeg Reserve.

We began our walk along the track leading to the Irish Peatland Conservation Council’s reserve at Lullymore, and walked through various habitats, such as wet grassland, poor fen, scrub, woodland, wet heath, and onto Lullybeg Reserve which continues the habitat diversity, especially wet grassland, elements of dry meadow, poor fen, marsh, wet and dry heath. This habitat richness means that a biodiverse fauna is expected, and we observed plenty of examples of this richness.

Drier areas showed good displays of Common Bird’s-foot-trefoil, a magnet for Burnet Companion moths, Narrow-bordered Bee Hawkmoths, Common Blues, and Dingy Skippers. This plant produces a ‘trefoil lawn’ at the base of the track opposite the reserve at Lullymore and near the silt pond on Lullybeg Reserve, and we stopped and spent plenty of time at both locations, seeing abundance and diversity. An especially lovely ‘blue’ female Common Blue loitered at the first patch of trefoil in Lullymore and we managed some great photographs of her; she posed nicely during the bright spells before becoming more active during direct sunshine. Many female Common Blues are chiefly brown on their upper surfaces, so seeing a blue individual is a treat. This blue suffusion usually features more prominently the further west you look, with more easterly areas having smaller, browner females.

The male is bright, shining blue wherever one looks for him, and these looked dazzling in the sunshine.

We checked the buckthorn bushes in the track connecting Lullymore and Lullybeg, seeing Brimstone eggs and half-grown larvae. Brimstones are good at breeding over an extended period, laying eggs from March into June. This results in adults emerging over at least two months giving the impression that it is on the wing most of the summer.

This is somewhat illusory. Individual newly hatched Brimstones spend little time on the wing during the summer; they hatch in summer, feed for a short time on flower nectar and disappear until the following March. Hatching over many weeks means it appears to be flying for several weeks, but no butterfly that needs to survive the winter as an adult can afford to take the risk that prolonged activity brings. That explains the seeming anomaly of seeing more in late March after winter than were counted the previous summer.  This brief summer fling also accounts for the excellent condition of the over-wintered Brimstone in March, when it is already around eight months old! After checking the Brimstone caterpillars, Emperor Moth caterpillars were found on Meadowsweet, one of several plant species it uses in the area.

Lullybeg Reserve was awash with Marsh Fritillary butterflies, most looking perfectly fresh. Confusion reigned along the stream bank, with Burnet Companions jostling with Marsh Fritillaries for space and attention, with occasional skirmishes between Dingy Skippers and Burnet Companions. Altogether I counted 99 Marsh Fritillaries. I am sure number 100 was seen by one of us!

We reached the silt pond which has an adjoining luxuriance of Common Bird’s-foot-trefoil, a fuel station for passing traffic and resident butterflies and moths alike. Nuzzling its furry way among the fragrant yellow blooms was a rather bumbling Narrow-bordered Bee Hawkmoth. An astonishing bee mimic, it is rarely bothered by avian predators but even if pursued, it is formidably elusive in full flight.

The increasingly scarce Small Heath butterfly joined in; it shouldn’t be in trouble, but like so much of our butterfly fauna, it is dwindling in distribution. The abundance of butterflies, moths, dragonflies (high numbers of Hairy Dragonflies and Four-spotted Chasers), and other groups at Lullybeg give a glimpse of what the wider countryside looked like, 30 or more years ago. There’s plenty wrong, but Biodiversity Week gives us the opportunity to admire what we still have and inspires us to nurture and advocate for nature. And so does the support we receive from people with a shared passion for nature, like those whose company we had the pleasure to enjoy on Saturday. Some members travelled from Cork and Tipperary for the event, so it was wonderful that the reserve’s bounty was on show, thanks to the great weather.

Thanks to everyone who attended, to everyone who worked on the reserve over the winter, and to Kildare’s Heritage Officer Bridget Loughlin who organised the county’s biodiversity week events.

Photos J. Harding

Here are five lovely butterflies to look for in May. See if you can find them and let us know about your record. See Butterfly Conservation Ireland’s Records Page  https://butterflyconservation.ie/wp/records/ for the details we need to report your sighting on Butterfly Conservation Ireland’s 2023 Record Page. The photographs below were taken in May 2023.

All photos J. Harding

Record rainfall in March, an indifferent April and the cool first two weeks in May provided the inauspicious meteorological backdrop to our Burren outings. Vegetation growth, butterfly abundance and emergence times are influenced by sunlight, temperatures and precipitation so expectations were tempered, despite the excellent habitats that we planned to walk.

Happily, Saturday gave us excellent weather especially in the morning after the mist dissipated and up to mid-afternoon after which it clouded over.

Our large, enthusiastic group of Burrenbeo Trust and Butterfly Conservation Ireland members assembled at Crevagh to walk the green road through Clooncoose Valley. This road mainly runs east/west so it is open to sunlight for much of the day, and along much of its length it is sheltered by stone walls and scrub making it an attractive corridor for commuting butterflies. The broad roadside also contains resources such as basking platforms, nectar and larval foodplants, while these are also present, albeit in more exposed situations, in the adjoining landscape. In short, it’s perfect!

And it is great for walkers too, with a fairly level surface and magnificent views. At the gate, I showed photographs of the butterflies we hoped to encounter and off we went, chatting and sharing observations and stories on our stroll.

A male Wood White soon fluttered into view, bobbing ponderously but purposefully over vetch-rich verges, seeking his mate. Previously netted and jarred Wood Whites were passed around, while the story of its place in the Burren was described. The delicate greenery on its hindwing underside distinguishes our Wood White from the examples found in Britain and Europe, with theirs showing grey undersides.  We spotted several more, all flying low or tasting nectar from wayside blooms. Ranked Vulnerable on the Irish red list, it felt reassuring to see it thriving here on The Burren’s Butterfly Road.

A companion species, in The Burren at least, is the even rarer Pearl-bordered Fritillary. This blue-eyed beauty is much sought after in Irish butterfly circles, with generations of butterfly lovers making the trek to Clooncoose to see it during the 100 years following its discovery in this area in June 1922. One dashed past, its deep orange uppersides drawing instant heed. One of our number netted the next commuter, another male. I jarred him to pass around, pointing out his blue eyes, deep orange upperside marked with velvety black chevrons, spots and lines, and his pearl-edged hindwing undersides. It is such a pleasure to see people’s reactions to a creature of immense beauty.

We released him and more appeared, and the green road became a catwalk with admiring photographers snapping basking, and feeding Pearl-bordered Fritillaries. All seen were males, all in perfect condition; the females were yet to emerge; this showed it was early in their flight season. This butterfly is highly dependent on weather conditions with emergence dates significantly influenced by prevailing temperatures. In warm springs, it hatches during April.

In a cool spring, this endangered butterfly will not be seen until May, and the lack of sightings at Fahee North the following day showed it to be significantly later than in several previous years, such as 2007 and 2009 when it was abundant during April.  According to data from UK Butterfly Monitoring Scheme, it has suffered a 72% abundance decline 1978-2019 and a deeply alarming 91% distribution decline 1982-2019. These are horrifying statistics. We don’t want to see this anywhere, but in Ireland the species is in the ‘Burren Only’ category so the Burren must continue to be treasured and managed according to its ecological need for open scrub on limestone.

Another must-see was the Dingy Skipper, represented in the Burren by subspecies baynesi, a paler form than found elsewhere, neatly adapted to its limestone homeland. This active creature was soon apprehended and passed over for inspection. A specimen from Kildare was shown for highlight the contrast in the depth of colouring. The uniqueness of the Burren form of this spring skipper provides a further impetus towards conservation of this magnificent landscape.

Green-veined White (the citral perfumed wings drew much interest) Small Copper (tiny but gorgeous), Red Admiral, Peacock, Speckled Wood were also viewed along with the butterfly-like Speckled Yellow moth, really abundant in Clooncoose. We were even treated to great views of an oblivious Red Fox, who couldn’t care less that he was under close observation.

The following day’s outing at Fahee North, near the Burren Perfumery involved a walk on a Marsh Fritillary breeding area on wet grassland and an adjoining area of scrub, limestone grassland and shattered limestone pavement. The weather was dry, with some sunshine but quite cool in a brisk westerly wind.

While butterflies kept their heads down during our outing, we did see great habitat that holds important populations. We saw a Marsh Fritillary caterpillar on a leaf of its foodplant, Devil’s-bit Scabious, and several Transparent Moth caterpillars on thyme growing on a well-developed ant hill. The Transparent Burnet is an attractive day-flyer, and very abundant in the Burren but rare elsewhere in Ireland.

We looked closely at the habitat and ecological needs of the Pearl-bordered Fritillary on the open scrub on the limestone adjoining the Marsh Fritillary breeding site, and why the continuum of habitat provided by a well-managed Burren is crucial to the long term survival of our rarest butterflies and moths.

It was a thoroughly enjoyable weekend, made special by the great company in the most special landscape Ireland has to offer.

Thanks to all who attended, especially to Pranjali from Burrenbeo Trust who helped to organize these events.

One of life’s annoyances is arriving back in Ireland after a break in a sunny clime to be told by a grinning neighbour, “The weather was amazing here when you were away. It only started to rain yesterday.”

Anticipating this scenario while in Malta, I checked the weather report and forecast for Ireland online on RTE Radio. Rain, wind, thunderstorms, flooding, etc, etc! No mention of sunshine! Just lots of the wet and windy stuff.

That morning I gazed through the window of the apartment in Għajnsielem, Għawdex (Gozo, nicknamed Il-Gżira tat-tliet għoljiet, the island of the three hills), at clear skies lit by the Mediterranean sun. The smug feeling that comes from knowing that I wouldn’t be on the receiving end of a meteorological putdown and that I was feeling that glorious Vitamin D delivering sunshine on my pale skin was delicious.

Gozo, also known by its residents as Għawdex is the second largest of the Maltese Islands, which are the sunniest in Europe with over 3000 hours of sunshine a year. The sun shines for about 300 days each year. The winter temperatures are benign, with highs of 16-18 Celsius on many days. The average annual temperature is about 23 Celsius. In Ireland, the average is 9.4 Celsius.  This is considerably lower than the average of 12.4 Celsius in Malta’s coolest month, February.

Temperatures in April this year (2023) reached around 23 Celsius, a comfortable heat. It rained once during my two-week stay. It gets hot later, with June to September regularly having temperatures in the 30s Celsius and sometimes higher. The highest temperature in 2022 was in August when 39.2 Celsius was recorded. Being surrounded by sea means the very extreme high temperatures seen on the European mainland are avoided. Rainfall is low compared with Ireland and occurs mostly during winter. Summer rain is very rare. The islands get about 600mm of precipitation per year, sometimes much less.

The inhabitants accommodate themselves to the high day-time summer temperatures by closing businesses from 11 am to 4 pm (typically). Heat can be troubling for those with an aversion to high temperatures so if that’s you, avoid visiting from June to September because you will not enjoy your stay. During these months, there is persistent heat, even at night.

The islands are special for their history, culture, and extraordinary architecture. The main island’s buildings were largely reconstructed after World War II when the island was essentially flattened by Axis bombing; Field Marshal Kesselring told the German High Command that “There is nothing left to bomb.”(Holland,  2003). The formerly iconic opera house in the capital Valetta (named after the French nobleman Jean de la Valette, who is recalled in the city’s name for his incredible feat in defeating the Ottoman invasion of Malta in 1565, one of the greatest sieges ever fought in Europe) remains a bombed ruin, a memorial to the devastation wrought on the island, a major strategic target in the Mediterranean war theatre.

For me, the islands are of immense interest, some of them rooted in the personal, given my Maltese heritage. The islands’ biodiversity is a big draw. As with isolated islands, the biodiversity count is lower than it is on continental land masses, but some of the species have developed unique characteristics, probably by being geographically isolated for thousands of years.

There are, for example, several endemic species and subspecies (an endemic is a species or subspecies that is confined to a restricted area) as well as near-endemics present, adding interest. Its strategic importance during conflicts also applies to biodiversity; it remains strategically important as a migration stop-over for many birds and insects.

The most eye-catching butterfly is Papilio machaon melitensis, the unique endemic subspecies of the swallowtail butterfly that occurs only on the Maltese Islands. Large, elegant and powerful in flight, it is undeniably beautiful. The subspecies rank of this butterfly was established in a study carried out by the University of Munich in 1936. Karl Eller researched the species based on specimens caught in September (probably the third generation).

Eller concluded that the Maltese swallowtail has a very long forewing, that the broad dark band running along the submarginal area of the forewing is strongly wedge-shaped and that this band, continued on the hindwing, is very broad there where it almost merges with the red spot. He also noted the finely scaled veins on the hindwing upper surface and found the red flame markings on the hindwing underside to be prominent. Eller considered the swallowtails he found in Malta similar in appearance to those in Africa.

Recently, Leraunt (2016) stated his belief that the swallowtail in Malta is in fact a different species of swallowtail, mainly found in North Africa and the Middle East: “Illustrations on the Internet of melitensis Eller from Malta convinced me that it is indeed P. saharae melitensis Eller, 1936, stat. rev.” This view that the Saharan Swallowtail occurs in Malta was challenged by Louis Cassar (2018) of the Institute of Earth Systems at the University of Malta:

Leraut does not provide convincing evidence based, for example, on morphometric analysis (the study of shape variation of organs and organisms and its covariation with other variables) or molecular characterization to substantiate his hypothesis.

Given Louis Cassar’s morphometric study of both species (all life stages), I concur with his view. Differences exist, for example, in the antennae, the size and shape of the red hindwing spot, overall size, the appearance and length of the pupal stage, egg size and larval colour and the length and colour of the osmeterium (this is an eversible forked organ concealed just behind the larva’s head that emits an unpleasant smell used to repel bird attacks). This does not mean that the Saharan Swallowtail never appears in Malta; given the nomadic habits of many swallowtails, it may occasionally migrate there from North Africa and from Lampedusa, an island about 150 km WSW of Malta where the Saharan Swallowtail was recently confirmed (Cassar et al. 2023).

Butterflies don’t care about their own taxonomic identity, but we must. Species confined to a small island group deserve study and may require protection and our appreciation as we marvel at the ability of nature to adapt to conditions that may differ significantly from those on a continent.

Certainly delightful, the swallowtail in the Maltese Islands appears to be successful, moving throughout the landscape and even island-hopping to seek mates and breeding sites. Netted with black veins and bands over yellow wings, the sharp blue hindwing band and flame-red spot and black tails spell sophistication. So does its behaviour. It flutters delicately above blooms while dipping its proboscis to suck nectar, then surges powerfully away, defying gravity and gale in its onward propulsion.

One of the loveliest sights is a primrose yellow swallowtail fluttering around red or purple Bougainvillea climbing on mellow yellow ochre Maltese walls.

This butterfly is oddly elusive. You can look for it for hours, be on the brink of admitting defeat and then see three at once, battling for possession of ground or pursuing a mate. The courtship is dramatic. The sexes flutter around each other before rocketing to an impressive height and then plummeting to pair on a low shrub. Territories are often held on a patch of ground containing larval foodplants and nectar sources.

Some of these are at altitude and may also function as hill-topping sites where territorial possession and mate-seeking may occur at the same time or transition to hill-topping behaviour. This is when some butterflies, especially males, fly for hours around an exposed elevated site, with little or even no clear or discernible purpose. Mates may be encountered at hill tops but in some species, this appears not to be the purpose; for example, Peacock butterflies that are in a breeding delay phase (diapause) have been seen hill-topping in the Burren.

The swallowtail in Malta breeds mainly on Fennel Foeniculum vulgare which occurs widely and is often abundant. Fennel is also a nectar source. Fringed Rue Ruta chalepensis is also used for breeding. According to online sources, the adult butterfly flies from late February until November. It passes the winter in the pupa.

When I visited in the last two weeks of April, the adults I saw were mainly very fresh specimens. I also found young caterpillars on Fennel. It is possible that I was seeing some second-generation butterflies by late April, but I am not sure. The larvae were, I presume, the offspring of the first generation and will be second-brood butterflies.

There were many butterflies flying in April. Small White, Large White, Eastern Bath White and Clouded Yellow were busy feeding and breeding. I saw Small White laying eggs on Caper Capparis orientalis, a lovely low shrub with striking flowers, especially the violet stamens. The flower buds are edible for humans.

Three blues were busy: Lang’s Short-tailed Blue, the Long-tailed Blue and the Southern Blue, previously believed to be the Common Blue. The classic migrants, Red Admiral and Painted Lady, were out too; some of the latter were faded and tattered, and others were perfect specimens.

The Wall Brown butterfly was abundant and I even saw a female on the main street in the Gozo capital, Victoria (Rabat). In Malta, none of these species needs very special habitats; they just need larval foodplants and nectar sources. I saw one Meadow Brown, on 29th April, near the coast east of Qala village. He was freshly emerged and I was excited to see it. However, the sight of what was recently a common butterfly should not typically evoke animation, but its populations on the islands are parlous:

A somewhat rare resident species that has experienced a sharp population decline in the last decade or so. The species still maintains small, fragmented populations in a couple of localities, but current trends do not bode well. (Cassar 2018)

The Meadow Brown exists in Malta as an endemic subspecies, Maniola jurtina hyperhispulla. Its extinction would therefore be especially tragic. The decline of this and other butterflies (Small Copper, Small Heath, Speckled Wood) might be linked with pollution, climate change and habitat loss, all in evidence on the islands. Chemicals are heavily used in farming to extirpate insects. Even in unfarmed land, bird trappers use persistent herbicides to remove vegetation from trapping sites. In recent years, precipitation levels have declined significantly below the average. The unrelenting building frenzy is swallowing precious land especially in Malta but also in Gozo.

Three ‘new’ butterflies have arrived on the islands in recent years. These are the Geranium Bronze Cacyreus marshalli, Dark Grass Blue Zizeeria karsandra and Desert Babul Blue Azanus ubaldus. The first occurs naturally in South Africa and may have arrived on imported Pelargoniums while the latter two are species of hot, arid lands, essentially eremic (desert) species. The survival of these three in Malta points, possibly, to the warming, drier climate there, and must be concerning for the habitats and native species currently supported.

All is not gloom. Maltese people are beginning to take their environment’s needs into account. A nature park covering 2.5 sq. km, Il-Majistral, was established in 2007 in the north of Malta. Malta has also declared protected areas covering about 29% of the land area and 35% of marine waters. No more bird-trapping licences are being issued, and shooting is less accepted now, but these activities continue. Some birds, like the Honey Buzzard and Marsh Harrier, are easy targets owing to their lazy, soaring flight. Further work will hopefully make shooting such species a thing of the past.

There is still much to see in the Maltese countryside, especially for a person from cooler climes unused to seeing the plant and insect life in the Mediterranean.

The friendliness and openness of Maltese people is a tonic too. A welcome is rarely if ever withheld. There is a distinctive culture. Signs of the religious culture are evident everywhere with churches in every village. Crucifixes hang in public places from government buildings to insurance offices. There is less restraint in speech, with a directness rarely heard elsewhere. The village is a key part of identity, and for many people the next village, a kilometre or two away, is considered a great distance to travel.

The squares are the centre of village life, and news travels fast. During the heat of summer, most social life occurs after dark, and the village squares come to life. Children chase one another around tables and street furniture and climb into niches in the baroque churches. Safe, friendly and memorable, you will certainly experience something different.

If there was only one thing I could change, it is the rampant construction of apartment blocks, which I would like to see ended. After that, I would ban pesticides. But that applies to Ireland too, along with massive fertiliser inputs.

Without a better way of managing food production, the glories of our world will continue to diminish. Wherever you visit this summer, try to visit sites with high nature value. The message that nature matters might hit home the better.

Photos J. Harding

References

Cassar, L. F. (2018). A Revision of the Butterfly Fauna (Lepidoptera Rhopalocera) of the Maltese Islands Summary. Naturalista Sicily, S. IV, XLII (1), 3–19.

Climates To Travel World Climate Guide (2023). Available at: https://www.climatestotravel.com/climate/malta (Accessed 06 May 2023)

Holland, James (2003). Fortress Malta: An Island Under Siege, 1940–1943. London: Miramax Books.

Ireland’s Blue Book (2023). Available at: https://www.irelands-blue-book.ie/IrishWeather.html#:~:text=Temperature%3A,C%20(60.3%20%C2%B0F (Accessed 05 May 2023)

Papilio machaon subsp. melitensis Eller, 1936 in GBIF Secretariat (2022). GBIF Backbone Taxonomy. Checklist dataset https://doi.org/10.15468/39omei accessed via GBIF.org on 2023-05-06.

Weber, Hans and Kendzior, Bernd (2006). Flora of the Maltese Islands A Field Guide. Marburg: Margraf Publishers.

Because butterflies are so loved and well-studied, there is good evidence of what butterfly species occurred in Europe, Britain, and Ireland over the past 100 years and further back, and the species that have flourished, declined, were gained, and lost.

For many countries in Western and Central Europe, the story is certainly very worrying. The countries that border the Mediterranean and those in the far north of Europe have suffered less decline and loss, but these areas are not without challenges that affect butterfly populations.

Since the early years of the 20^th century, England has lost the Mazarine Blue (possibly c.1903 but may have disappeared in c. 1865), Black-veined White (1923), Large Tortoiseshell (c.1950), Large Blue (1979), and Chequered Skipper (1975). The Large Copper was lost c. 1864, due entirely to habitat destruction.

In the UK, the Duke of Burgundy, High Brown Fritillary, and Heath Fritillary are in serious trouble and the High Brown Fritillary, in very deep trouble, may be lost. Several other species are falling in abundance and distribution there, including the Marsh Fritillary, Pearl-bordered Fritillary, and Small Pearl-bordered Fritillary. Just to take the statistics for one butterfly, the Wood White. This elegant, dainty creature has fallen by 82% in its population and 76% in its distribution during the period 1979-2019.

You will see from the dates that butterfly declines and losses have been taking place in England for a long time. The situation is also very depressing in parts of central Europe. The northern Belgian province of Flanders has seen steep losses. 20 butterflies have become extinct (29% of its species list), and between 1992 and 2007 overall numbers declined by around 30%. A study published in the early 2000s found that 18 species (28% of its list) were threatened with extinction. In the Netherlands, 20% of species have become extinct, and since 1990 overall numbers in the country declined by 50%. Denmark and the Czech Republic are in the same sorry category of loss and decline suffered by Belgium and the Netherlands.

Just to give an indication of how grave the situation in the Netherlands is, consider the fact that the Silver-washed Fritillary, thriving in Ireland and rising in abundance in England is in deep trouble there. The Dingy Skipper, holding steady in the UK and Ireland, is very rare in the Netherlands. The Marsh Fritillary is now extinct in the Netherlands.

Countries in Europe were ranked in 2019 in the Journal of Insect Conservation according to their butterfly red lists where species are ranked under threat categories. There are five rankings, excluding countries that lack data.

The next group of countries is in a loss category below that occupied by Belgium, the Netherlands, Denmark, and the Czech Republic. These are Germany, Austria, Poland, Slovakia, Romania, and the UK.

Ireland is ranked in the next group of countries; we are mid-table for losses, along with countries such as Ukraine, Switzerland, Hungary and Finland.

The two countries that fare the best, with the lowest declines, are Spain and Italy.

Chris Van Swaay, one of Europe’s most eminent butterfly experts, explains the declines in the Netherlands.

“Before 1950 or so, grasslands in the Netherlands very much resembled what we now only have left in some nature reserves – they were wet, they had lots of flowers, were lightly grazed and mown only once or twice a year. This was very low-intensity farming.

“In two decades after the 1950s, the countryside was rebuilt – land was drained and planted with one species of grass, large amounts of fertiliser was put on the land, and it was mown six times a year. There is no room for butterflies except on road verges and nature reserves. The countryside is more or less empty.”

The reasons for the declines in Europe, Britain and Ireland are quite similar and often the same. Modern farming methods are the greatest causes of decline and loss. These methods have caused massive habitat loss and degradation with large areas of our land mass devoted to production of one crop species with no room for any other plant. In areas where this has not happened, traditional farming methods that maintained biodiversity have fallen out of use, creating successional changes that have lost us heathlands and grasslands, while the cessation of traditional woodland management has changed woodlands, resulting in closed canopies and darker woods unsuitable for many woodland species.

The loss of habitats for other reasons, such as building, afforestation, land drainage, and peat mining has also contributed to losses.

More recently, the concern is growing about the impact of chemical pollution, which can damage habitats that are not directly affected by changes in farming practices or habitat destruction. The deposition of nitrogen from the air is believed to be responsible for changing the character and chemical content of vegetation, making the habitat and foodplant unsuitable for butterflies. This is a sinister threat because it can affect populations that occur a long distance from industry and intensive farming. It is also difficult to address, requiring, probably, a geographical-scale response, not simply a local or national strategy to reduce air pollution.

Climate change is a further challenge; this is complex because some species are beneficiaries of a warming climate, while others suffer. Cold-adapted species are driven further north or uphill, and warmth-loving species are extending their range northwards. A mismatch between the development of vegetation and emergence or breeding times may be driving declines in some areas. For example, increasing dryness and heat in the Mediterranean region may deprive some species of nectar and foodplants. Extreme climate events associated with climate change can have dramatic and sudden impacts. The Green-veined White’s abundance in many areas of Ireland crashed in 2019 following the drought in 2018.

How do we deal with the threats to our butterflies?

We need policies and actions that reverse the damage described above.

Greening our urban and suburban spaces by allowing vegetation to grow and planting native plants from local seed will help. Avoid tidiness; relax management in gardens, parks, verges, and the grounds of businesses. Do not use chemicals in these areas.

Reserves will not save butterflies unless they are large and managed. Many protected areas are too small and are often badly managed and being damaged. Landscapes must be protected, and these must contain a range of habitats. A good example of where this is done is the Burren in Counties Clare and Galway.

Pollution must be tackled. Massive chemical inputs in agriculture and reseeding grassland is destroying nature in general. Monoculture grasslands should be replaced with multi-species swards generated by allowing the seed bank in the soil to germinate. In areas where intensive farming is needed, ‘wild’ land must be incorporated into the landscape, typically as unfarmed extended field margins adjoining hedgerows and wood edges.

Woodlands containing native trees grown by allowing woods to extend naturally would add habitat diversity, as would maintaining wide rides allowing light in the woods. New woods must not be grown on high nature value semi-natural grassland, heaths, and bogs. New woods should be planted on intensively managed farmland. Scrub must be allowed to develop at the margins of woods rather than having a sharp edge where woodland transitions directly to open grassland.

Encourage a love of nature in everyone. Most focus is on youth education, naturally, but highlighting the intrinsic importance and wonder of nature should be promoted at all levels of the population. Participate in citizen science monitoring of butterfly populations to help to build knowledge of the status of butterfly populations. Getting involved in conservation organisations is important because these do important practical conservation, monitoring and education. These organisations help to influence policy in favour of caring for our environment.

Most of our countryside looks the way it does because it is heavily plied with chemicals. Fields of uniform, sharply green sward without flowers is not the ‘natural way.’ Fertilisers exclude flowers by promoting accelerated grass growth and in some cases, by providing a  chemistry that kills flowers. Herbicides kill any flowers that remain. There is certainly no need for our gardens, parks, and hedge margins to look like this. Make sure your patch doesn’t.

References

Maes, D., Verovnik, R., Wiemers, M. et al. Integrating national Red Lists for prioritising conservation actions for European butterflies. J Insect Conserv 23, 301–330 (2019). https://doi.org/10.1007/s10841-019-00127-z

Warren, M.S., Maes, D., van Swaay, Chris A M, Goffart, P., Van Dyck, H., Bourn, N.A.D., Wynhoff, I., Hoare, D. & Ellis, S. 2021, “The decline of butterflies in Europe: Problems, significance, and possible solutions”, Proceedings of the National Academy of Sciences – PNAS, vol. 118, no. 2.

Thomas, J. and Lewington, R. (2014) The Butterflies of Britain and Ireland. (Revised edition) British Wildlife Publishing, Dorset.

https://www.theguardian.com/environment/2019/apr/01/butterfly-numbers-fall-by-84-in-netherlands-over-130-years-study

https://www.gbif.org/dataset/f9af6ffd-febc-4626-b2e8-809b1c60fa01#description

Last August we reported the latest information concerning the state of Ireland’s butterfly populations. The picture painted by the Irish Butterfly Monitoring Scheme data for 2020 and 2021 was not positive, with no species showing positive trends in 2021 with only two, the Brimstone and Peacock, showing a stable trend since 2008, the baseline year. The most recent data from the UK is now available. 

In this article, we present the overall data for the UK report, the data for some of the species found in both the UK and Ireland, and comment on the findings.

Key findings of “The State of the UK’s Butterflies 2022”

In the UK, long-term trends show that 80% of butterfly species have decreased in abundance (the number of butterflies) or distribution (the areas where butterflies occur), or both since the 1970s. By comparison, 56% of species increased in one or both trends. These findings are very similar to the headline results of the previous assessment in 2015. As then, the report finds that there are winners and losers but, on average, UK butterflies have lost 6% of their total abundance at monitored sites and 42% of their distribution over the period 1976-2019. Considering only the changes that assessors have most confidence in (those that are statistically significant), almost twice as many UK species have decreased in at least one measure than have increased: 61% have decreased and 32% increased.

Most habitat specialist species, (species restricted to particular habitats such as flower-rich grassland, heathland and woodland clearings), have declined dramatically in the UK. As a group, their abundance has decreased by over one-quarter (-27%) and their distribution by over two-thirds (-68%) since 1976 (1976 is the baseline year used for UK butterfly monitoring; in Ireland, it is 2008). Wider countryside species, butterflies that can breed in the farmed countryside and in urban areas, have fared less badly, although as a group they have decreased since 1976 (-17% in abundance and -8% in distribution).

Multi-species indicators provide an overall summary of changes in either abundance or distribution by combining species-level indices for groups of butterflies sharing particular attributes. The report authors constructed abundance and distribution indicators for all butterfly species (including the common migrants), and separately for resident species classified as habitat specialists or wider countryside species, at the UK level and for each of the UK countries, where there were sufficient data. Multi-species indicators for abundance and distribution were also produced for Butterfly Conservation’s Priority Species at the UK level.

Multi-species distribution indicators at UK and country levels were also constructed by combining occupancy indices in three ways: for all species, for habitat specialists and for wider countryside butterflies.

Long-term UK abundance trends

Analysing the standardised count data from the UKBMS generated long-term trends for 58 species. UKBMS is the UK Butterfly Monitoring Scheme. It uses data gathered from transect walks, which uses the same methodology used by the Irish BMS in which recorders walk a fixed route (transect) in good weather each week from 1 April to 30 September and count every butterfly in an imaginary 5m box. Overall, more species decreased than increased in abundance: 30 species (52% of the total) had negative trends and 28 species (48%) positive trends. The statistical significance of trends provides a measure of the confidence that we should place in the changes they show. We can be much more certain that species with statistically significant trends have genuinely changed in abundance, irrespective of how large or small the change is. The UK long-term trends show that 19 species (33% of the total) have decreased significantly in abundance, 15 species (26%) have increased significantly and 24 species (41%) have non-significant trends. Only slightly more species decreased in abundance than increased at UKBMS-monitored sites. This represents a small improvement in the fortunes of UK butterflies compared to the previous assessment in 2015, when 36% of species with long-term abundance trends had decreased significantly and 23% had increased significantly.

Long-term UK Distribution Trends

Occupancy modelling of Butterflies for the New Millennium (BNM) species occurrence records was used to produce long-term UK distribution trends for 58 species. This method uses non-standardised recording, where recorders log any life cycle stage of any butterfly species, anywhere in the UK on any day of the year. This flexibility encourages large numbers of contributors leading to very widespread coverage of the UK landscape every year. This is the same system used by Butterfly Conservation Ireland’s recording scheme; see https://butterflyconservation.ie/wp/records/.

Overall, 43 species (74%) had negative distribution trends and 15 species (26%) positive trends. Far more species have decreased in distribution than have increased. The same pattern is found just for those species with statistically significant distribution trends: 30 species (52% of the total) had significant decreases in distribution, eight species (14%) significant increases and 20 species (34%) showed changes in distribution that were not statistically significant. Nearly four times as many species have decreased significantly in distribution as have increased. The occupancy modelling approach used differs from that in the 2015 assessment, so a direct comparison is less valid than for the abundance trends. However, fewer species show significant distribution trends (both decreases and increases) now compared to the 2015 report.

Combined Assessment (Abundance and Distribution)

Considering just the statistically significant trends, 36 species (61%) had decreased significantly in one or both trends and 19 species (32%) had increased significantly in one or both. Almost twice as many species had a significant negative trend in at least one measure than had a significant positive trend in one or both.

Although it remains widely distributed, mainly around the UK coastline, there is increasing concern about Grayling, which has suffered a severe long-term decline. Since 1976, the abundance of this species has decreased by 72% and its distribution by 92% at the UK level, and with major declines in both measures in England, Scotland and Wales. The data from Northern Ireland was insufficient to produce trends. These ongoing, rapid declines recently led to Grayling being upgraded from Vulnerable to Endangered on the GB Red List. Dependent on fine leaved grasses growing in sparse vegetation with much open ground or rock, the butterfly faces threats from habitat degradation due to ecological succession and nitrogen deposition, and from consequent small population size and increasing isolation.

The trends for Large Heath, another Priority Species, provide a positive picture, with a very large (407%) increase in abundance at monitored sites and little change in distribution (-2%) since the 1990s. Although present in all four UK countries, the remote location of most colonies means that few are monitored, and data are only sufficient to produce a UK-level abundance trend. Many of the monitored sites are managed for biodiversity and Large Heath populations have benefitted, for example from peatland restoration on lowland bogs in Scotland. However, there are concerns elsewhere in its range. For example, at some sites on the North York Moors and in Northumberland, there has been a substantial reduction in the amount of cottongrasses, the Large Heath’s larval foodplants, perhaps due to climate change. In many other areas, particularly in the uplands, data on how the butterfly and its habitats are faring are lacking.

Marsh Fritillary is the focus of conservation efforts in all four UK countries. Its distribution has decreased by 43% since 1985.

The report then focussed on the individual countries in the UK.

England

In England Wood White has decreased by 82% in abundance (1979-2019) and by 77% in distribution (1992-2019), is classed as Endangered on the Red List and is a Priority Species for Butterfly Conservation. Most of the long-term abundance decline took place during the 1980s and recent signs are more positive, thanks to intensive conservation efforts in many parts of the Wood White’s range.

Northern Ireland

The multi-species indicators for Northern Ireland’s butterflies show decreases of 17% in abundance (2006- 2019) and 10% in distribution (1993-2019). However, only about half of the resident and regularly breeding butterfly species in Northern Ireland had sufficient data to calculate long-term trends up to 2019, so these indicators are not necessarily representative of all butterflies. In particular, habitat specialist species that are of conservation concern in Northern Ireland, such as Large Heath, Small Blue and Dingy Skipper do not, as yet, have sufficient monitoring coverage to produce trends. (The Small Blue and Dingy Skipper have highly restricted distribution in Northern Ireland, especially the Small Blue.)

The Wall butterfly has suffered a precipitous decline in Northern Ireland and appears to be on the verge of extinction. Formerly found in all six counties, a rapid decline since the 1990s reduced the species to the coastline of Co. Down, where there were only three records in the period 2015-2019. A single Wall was also seen in 2021, so the species is still clinging on. The cause is not known with any certainty, but the decline mirrors that experienced by Wall in England and Wales, where it is also among the most severely declining butterfly species, and in other parts of Europe.

Small Heath is another species, like Wall, which is associated with short, sparse turf, and which has undergone a rapid distribution decline (40% decrease 1995-2019) in Northern Ireland. Indeed, Small Heath has decreased significantly in all four UK countries. Loss and deterioration of habitat seem the most likely drivers of this decline, with factors such as climate change and nutrient pollution stimulating greater vegetation growth resulting in longer, denser swards even on sites managed for biodiversity. Small Heath caterpillars fail to survive on grasses when fertilizers are applied at the levels typically used in intensive agriculture, which suggests that the species may also be harmed away from farmland by smaller amounts of atmospheric nitrogen pollution.

Dingy Skipper declined by 15% in abundance and 35% in distribution 1976-2019.

Orange-tip declined by 26% in abundance and 1% in distribution 1976-2019.

Small Copper declined by 39% in abundance and 37% in distribution 1976-2019.

Small Tortoiseshell declined by 79% in abundance, but its distribution increased slightly up 0.2% 1976-2019.

Comma increased by 203% in abundance and 94% in distribution 1976-2019.

Silver-washed Fritillary increased by 284% in abundance and 1% in distribution 1976-2019.

Regarding Cryptic Wood White Butterfly Conservation UK’s new analyses provide a more optimistic picture with nonsignificant trends suggesting an increase in abundance over the past decade and a stable distribution trend from 1993-2019. Unlike Wood White, which is mainly a woodland species in the UK, Cryptic Wood White uses more open habitats such as grasslands, and colonies are at risk from urban development and agricultural intensification. Other species that appear to be experiencing recent upturns in their fortunes, even if data are currently insufficient to demonstrate it quantitatively, include Dark Green Fritillary, Silver-washed Fritillary and Holly Blue. All three appear to be continuing to expand across Northern Ireland, where suitable habitats exist.

Discussion

There are strong similarities in the population declines and increases seen in the UK and the Republic of Ireland. Looking at the species that occur across these islands that are under pressure, most are species that occur on grassland. Grayling, Gatekeeper, Small Heath and Wall breed on grasses, which are almost certainly being affected by agriculture and industry adding nitrates to soils. This is being done directly, by the application of fertilisers and indirectly, by nitrates arising from farming, nylon manufacture and burning fossil fuels deposited from the atmosphere on soils, either in precipitation or as trace gases and particulate matter. There is good evidence that this is poisoning larvae feeding on nitrogen-enriched foodplants and cooling the temperature around the foodplant, which prevents or slows larval development. There is evidence that some non-grass feeders, like the Small Copper, which breeds on sorrels, are poisoned by fertiliser uptake by the foodplant.

The fact that declines are noted in areas where there is no agricultural activity suggests atmospheric pollution. There is very little farming activity along the Dublin coastline, and the Grayling and Wall are extremely rare on the coastal dunes where they used to be abundant and well distributed.

Quite concerning is the information from Department for Environment, Food and Rural Affairs (DEFRA) that the largest amounts of wet deposition inputs of nitrate (NO₃^–) and ammonium (NH₄⁺) (deposited from the atmosphere by rain and snow) are found in the uplands of Wales, northern England and western Scotland, away from industrial areas.

Nitrogen transformation and plant uptake of mineral nitrogen involve the production and consumption of protons and can, therefore, contribute to soil acidification. Where this occurs, plants that occur only or chiefly on alkaline soils, such as Kidney Vetch and Common Bird’s-foot-trefoil, may disappear, impacting on butterflies that breed on calcicoles (plants that need lime-rich soil), such as Small Blue and Common Blue.

There is also evidence that the poor recovery of sensitive species of Sphagnum moss in the southern Pennines (Lancashire and Yorkshire) is largely due to toxicity of ammonia NH₄⁺ and nitrate NO₃^– deposition. Loss of moss and lichen species in Cumbria over the past 30-40 years may also be due to increased nitrogen deposition over that period. This has implications for the health of our bogs, and for the Large Heath which relies on peat bogs for its survival.

The loss of Marsh Fritillary populations in the UK appears to be due to loss of habitat. This is where habitat is simply removed by agricultural intensification such as ploughing and reseeding. Habitat loss is also taking place in Ireland, where land drainage, agricultural ‘improvement’ and afforestation is taking a toll, but natural succession, where scrub and woodland is developing on grassland no longer grazed, and on cutaway bogs where machinery disturbance has ceased and scrub develops, is also resulting in habitat loss.

There is some good news. The Small Tortoiseshell, its abundance in decline in the UK (-79%), appears less affected here. Between 2008 and 2021, it declined in abundance by 49%. A new enemy, Sturmia bella, a parasitoid fly that colonised Britain from the continent has affected Small Tortoiseshell populations. This fly has not been recorded here, but it is possible that Irish and British (but probably not Northern Irish) populations are being reduced in abundance by drought conditions that force the butterfly to enter hibernation in mid-summer and cancel a second generation typically seen in September.

Better news is the advance of the Silver-washed Fritillary, thriving in new woods developing on cutaway bogs and abandoned farmland. This handsome butterfly increased in abundance in the UK but has not notably risen in distribution there; it has, it appears, always been more widely distributed in Ireland.

The Comma is thriving in the UK. It is one of the outstanding successes there, and it is rapidly expanding its distribution here, having begun its colonisation of Ireland in the early 2000s. The Comma appears to be benefiting from the warming climate and may also be thriving on nitrogen-enriched Stinging Nettles, its main larval foodplant. We now know that it is double-brooded in Ireland, and this may be boosting its colonisation.

The story of the fate of our butterflies is a developing narrative, with diverging fortunes for the cast of characters that comprise our butterfly fauna. Unless we continue to monitor our populations, we will lose the thread of the plots, and may lose our focus altogether. Having some very rare species, like the elegant Pearl-bordered Fritillary, which occurs only in parts of the Burren, we need to maintain our monitoring and conservation focus. The UK has seen a decline of 64% in abundance and a disastrous 88% in the distribution 1979-2019.  A leading butterfly scientist, Professor Jeremy Thomas, commented in 2010: “Unbelievably for entomologists of my generation, the butterfly is extinct in Dorset, Kent and Somerset…reduced to single sites in Surrey and Gloucestershire.”  In Ireland, the Pearl-bordered Fritillary only occupies ten 10 km squares. We cannot such losses to happen here.

References

Fox R, Dennis EB, Purdy KM, Middlebrook I, Roy DB, Noble DG, Botham MS & Bourn NAD (2023) The State of the UK’s Butterflies 2022. Butterfly Conservation, Wareham, UK. Available at https://butterfly-conservation.org/sites/default/files/2023-01/State%20of%20UK%20Butterflies%202022%20Report.pdf

Harding, J. (2021) The Irish Butterfly Book. Privately published, Maynooth.

Judge, M and Lysaght, L. (2022), The Irish Butterfly Monitoring Scheme Newsletter, Issue 14.

Nash, D., Boyd, T. and Hardiman, D. (2012) Ireland’s Butterflies a review. Dublin Naturalists’ Field Club, Dublin.

Thomas, J. and Lewington, R. (2014) The Butterflies of Britain and Ireland. (Revised edition) British Wildlife Publishing, Dorset.

https://butterflyconservation.ie/wp/2022/08/29/irelands-butterflies-continue-to-decline/

https://uk-air.defra.gov.uk/assets/documents/reports/empire/acidrain/nitdep.html#:~:text=A%20key%20effect%20of%20N,indicators%20of%20increased%20N%20deposition.

Today’s Irish Examiner has a feature concerning the use of artificial lawns. The introduction followed by Butterfly Conservation Ireland’s contribution to the feature article is shown below.

The full article is available at

https://www.irishexaminer.com/lifestyle/outdoors/arid-41106382.html

Plastic grass: Low-maintenance fuss-free greenery — or a menace to the environment?

CAROLINE DELANEY examines the backlash against synthetic lawns, and asks environmental experts for their observations

It’s sold as low-maintenance, fuss-free and durable. And artificial grass is definitely gaining a foothold here. There are dozens of plastic grass specialists across the country offering ‘instant lawns’ to playschools, cafés, hotels, and homeowners. Then, there’s the DIY option with retailers such as Co-Op Superstores, Homestore & More, and Woodies — and even carpet outlets — offering grass tiles or rolls of artificial grass which can be laid in a manner similar to carpet.

SUSTAINABILITY & CLIMATE

Check out our Sustainability and Climate Change Hub where you will find the latest news, features, opinions and analysis on this topic from across the various Irish Examiner topic desks and their team of specialist writers and columnists.

But when we have an official biodiversity emergency as noted by the Dáil in 2019 and the Citizens’ Assembly on Biodiversity Loss in 2022, and when there is a commitment in the Programme for Government to tackle the climate and biodiversity crises, is there still a place for artificial grass?

Bloom controversy

Artificial grass has been banned from Chelsea Flower Show but, controversially, showed up in displays at Bloom here in Ireland last year. However, this year there will be no plastic grass at Ireland’s largest garden festival which this year takes place from June 1 to 5.

A Bord Bia spokesperson confirmed: “Bord Bia Bloom actively discourages the use of artificial grass in any on-site activation from sponsors on-site, and there are no artificial grass providers registered to exhibit at this year’s event.”

The garden designers at Bloom are also unlikely to use plastic grass this year, the spokesperson said: “Bord Bia Bloom actively encourages show garden designers to use natural materials where possible.”

Referring to last year’s festival when some visitors and environmental experts said they were disappointed to see plastic grass on display, the spokesperson said: “There are some instances, such as at last year’s event where an exhibitor requested that a very small section of an accessible garden feature artificial grass as natural grass would not have supported the weight of a mechanised wheelchair. However, we strongly recommend to all of our designers that they incorporate natural, sustainably produced plants and grass in their gardens.”

This follows moves in recent years to ban artificial turf from the Chelsea Flower Show which this year runs from May 23-27, and other events run by the Royal Horticultural Society. The RHS, Britain’s leading gardening charity, said no fake grass would be allowed because of its damaging effect on the environment.

What the experts say

Overwhelmingly, experts in biodiversity and environment are calling to ban the use of plastic grass, or put prohibitive tax on it.

Jesmond Harding

The installation of artificial lawns and shrubbery offers convenience but nothing else. The materials used contribute to pollution and the finished product offers nothing but damage to biodiversity. Synthetic plants are made from petroleum and fossil fuels used in their manufacture generate pollution that damages soils, plants, insects, birds, and mammals. Visually, the effect is ugly, and reflects a lack of care for the natural environment. It highlights the disconnect from nature and the idea that natural surroundings are inconvenient rather than a source of wonder and pleasure. I have observed an increase in the use of artificial lawns and plastic shrubs in tubs, and my reaction is to ask why. What is the appeal?

Jesmond Harding is the author of The Irish Butterfly Book.

Artificial plants look tasteless and cheap. Even those that appear lifelike show an unvarying flat, empty gleam. Sanitising one’s surroundings might be a motivation. Bizarrely, the use of artificial lawns is promoted as a response to climate change, as these do not need watering during drought. The irony of promoting materials that produce climate-warming gases as a solution is exasperating and perverse, an offence to common sense.

There has been an incremental advance in the appearance of synthetic plants. We used to see artificial house plants, such as lilies for indoor vases, progressing to potted shrubs and now to outdoor shrubs and lawns.

On one journey through a local housing estate, I counted the number of hard surfaces replacing grassed gardens, which proved to be two-thirds of the outdoor spaces observed. This trend appears to be influencing new housing developments, with hard-surfaced front gardens or with no front-of-house space, just adjoining on-street parking slots.

There are studies that show links between the decline in butterfly species and atmospheric nitrogen deposition, some of this caused by burning fossil fuels to make artificial plants.

There is no pressure to produce food crops in gardens, so there is no need to apply nitrogen fertilisers which create nitrous oxide, a greenhouse gas that has 300 times the heating power of carbon dioxide. Gardens can be a haven for species fleeing the onslaught of chemically-mediated farming, but only if we grow native grasses, flowers, shrubs and trees in our gardens.

Butterfly Conservation Ireland has found that about half of our butterfly species visit butterfly-friendly gardens, and around one-third of our butterflies breed in gardens containing the right plants and conditions.

A plastic garden has no appeal for our wildlife.

The convenience argument for artificial grass can be answered by using low-maintenance alternatives such as pea gravel sown with drought-tolerant native plants such as kidney vetch, bloody cranesbill and Common Bird’s-foot- trefoil — all great for pollinators and providing a long flowering period giving colour and texture from May to October. There is no such thing as effortless management.

The Irish Butterfly Book: A Complete Guide to the Butterflies of Ireland by JM Harding.

While spot weeding is needed in a gravelled garden, it is also a requirement in artificial turf, where weeds will appear, despite the promise of maintenance-free convenience.

I would like to see the use of artificial plants banned or at the very least subject to high taxation to take account of the environmental damage involved in the production and use of such material. The use of such materials accelerates biodiversity loss; any activity that creates environmental damage should be discouraged or banned.

Jesmond Harding is the author of The Irish Butterfly Book and runs the charity Butterfly Conservation Ireland.

This week will have unsettled weather with plenty of cloud and rain. These conditions do not allow our longest-lived butterfly, the Brimstone, to emerge from its over-wintering quarters to begin its breeding cycle. Late in March is typically when it emerges to seek mates, feed and begin to look for breeding plants.

The Brimstone has one generation a year. In Ireland and Britain, eggs are laid during spring and early summer on two small native trees, Purging Buckthorn and Alder Buckthorn. Purging Buckthorn is found mainly on rocky ground in the midlands and west of Ireland, but also on fen peat on cutaway bogs and in hedges on lime-rich soils. Alder Buckthorn occurs mainly on boggy soils, especially in alkaline peat on cutover bogs and fens, in and at the edge of bog woodland, on moist heaths and limestone pavement. Both plants occur together in some places, such as in and at the edge of turloughs in the west of Ireland, notable in the Burren.

These trees have a highly localised distribution in Ireland with Alder Buckthorn much the rarer of the two plants. The only region where these tree species are relatively abundant is the Burren, in County Clare and Galway, the only area in Ireland where the Brimstone is plentiful. Elsewhere, the Brimstone occurs in scattered locations mainly across the midlands. The butterfly does not occur in Northern Ireland, the northwest, or the southeast and is very rare in the east and southwest. The butterfly breeds only where its breeding plants occur but it does not occur in every place its larval foodplants are found.

After mating and laying eggs in spring and early summer, the adults die off, but quite slowly, with some surviving as late as early July. During July and August, the new generation is emerging as adult butterflies, but unlike most of our butterflies, they do not breed until the following spring after hibernation is complete.

So how does the Brimstone deal with several months when breeding is impossible, when the weather is unsuitable, and food is unavailable?

The article looks at how the Brimstone manages to survive adverse conditions and why it appears to be more numerous in spring after hibernation than it was during the previous summer.

The Brimstone, unlike most of our butterflies, is sexually immature when it hatches from the pupa. A reproductive diapause occurs in this butterfly. Diapause is the suspension of development or activity in any life stage of a butterfly. This strategy is used to survive months of unsuitable weather which often corresponds with the period during which its breeding plants are unsuitable. Diapause is a rest period undertaken by butterflies, moths and other insects with a seasonal life cycle.

Diapause aligns the butterfly’s complete life cycle to seasonal changes in the environment to ensure that further development occurs in the most suitable conditions. Diapause is controlled by the neuro-endocrine system (hormones released by the nervous system). Furthermore, it is genetically determined for each species and once initiated, it is not influenced by surrounding climate developments, even when these are favourable for development. Diapause usually occurs in response to environmental stimuli that precede unfavourable conditions, such as declining hours of daylight (Nash et al. 2012).

In the case of the Brimstone, diapause occurs in the winged butterfly and takes the form of delayed sexual maturity. This is likely an adaptation to the coldest months of the year and the condition of the foodplants from July to April. Between July and October, buckthorn leaves are tougher than they are in April-June and perhaps contain toxins making them unsuitable for the larvae. In March and well into April, leaves have yet to appear on the plants.

In males, sperm develops during summer and autumn but the duct through which sperm passes during mating is narrow and contains few sperm before hibernation, but the duct is swollen and filled with sperm after hibernation. Female Brimstones hatch without developed eggs (which are small, unyolked and without an outer membrane), and these are fully developed only after the females spend several warm days on the wing in spring after hibernation.

Given that males are sexually mature immediately after emerging from hibernation, males immediately seek mates. However, females do not begin emergence at the same time as males. The males spend several days on the wing before the first females appear.

This mismatch in emergence is not unusual in Ireland’s butterflies. In most if not all our butterflies, males emerge first. What is the advantage of this pattern of earlier male emergence?

The advantage is that the females are located quickly and mated, and they can concentrate on laying their eggs. In most of our butterflies, females hatch from their pupae with fully developed eggs so laying starts soon after mating.

But the female Brimstone is not ready to lay her eggs on emerging from her pupa or even after several months of life, including for a period in spring after hibernation.

Yet there must be an advantage for male Brimstones to emerge earlier from hibernation. What this might be, appears to be unknown. Here are some possibilities. Female Brimstones, it appears, mate once, while males certainly mate with as many receptive females as possible. It might be an advantage for males to emerge earlier to seek females, including females that have yet to emerge from hibernation. The earlier the male emerges, the more mating opportunities he has.

Furthermore, it is possible that the older he is, the more fertile he becomes. It has been shown that the male Monarch butterfly Danaus plexippus older males produce a higher ejaculate mass, which means females receive more nutrients from older males, increasing female reproductive productivity (Wicklund et al. 1996).

Are there advantages for female Brimstones of earlier male emergence? It is possible that male Brimstones may be sensitive to pheromones released by other males during mating. This might mean that recently mated females are less attractive and less likely to be courted by males, allowing these females to develop and lay their eggs without the inconvenience of male harassment and the dangers associated with prolonged, conspicuous male attention, which must draw attention from birds and other animals.

An advantage for later female emergence is that the foodplants have extra time to develop. In March, neither of its foodplants is in leaf so food is unavailable for the caterpillar. By the time females are ready to lay, the leaves are further on in their growth, although the leaves are often unavailable until well into April. In cool spring conditions, eggs take longer to hatch, and this delay should help the larvae to appear when the leaves are available. It is important that newly hatched larvae have young, tender leaves, so synchronizing emergence, egg development, mating and egg laying with the development of the foodplant is very important.

Before adult butterflies hibernate, they must feed on nectar (and, in some species, fruit, and tree sap) to build reserves to survive the colder months without food. However, the Brimstone butterfly shows some surprising results. Release and recapture experiments in Sweden show that wild Brimstones put on weight within one or two weeks of first being caught but that when caught later weight did not increase but was maintained at a steady rate. Despite males having to devote resources to developing their reproductive system over winter males have not been observed to feed more than females before hibernation. It might be expected that having to devote resources to reproduction over the winter would reduce male survival rates. However, both sexes have similar winter survival rates (Wicklund et al. 1996). As far as I know, this has not been explained.

The Brimstone shows other unusual characteristics. A study carried out in central Spain during the period 2006 to 2012 looked at uphill and downhill migrations of the Brimstone. These movements are influenced by the resource needs of the butterfly at different times of the year and by temperature during the summer, in this case, the need to avoid extreme heat downhill. One aspect that surprised the researchers was the abundance of over-wintering Brimstones was higher than it had been the previous summer because the numbers must decrease during hibernation (some die of starvation, and some are eaten).

It is ecologically impossible that the population of a single-brooded over-wintering butterfly is higher in spring than in the previous summer before it over-wintered. The researchers rule out the possibility of immigration boosting abundance (the Brimstone is not a migrant) and state that the reason is unknown but it may be linked with differences in behaviour in summer and the following spring. They state that “reduced summer activity could also make (it) difficult to quantify potential downhill movement in late summer” (Gutiérrez, D., & Wilson, R. J. 2014)

While the Brimstone will behave differently under the climatic conditions in a mountainous region in central Spain and in a lowland area in Ireland, it is possible that the researchers miss an important detail about the Brimstone’s behaviour during the summer.

I have often been struck, as have others, by the often excellent condition of Brimstones in March and early April. Some individuals look pristine, very few have faded and tattered individuals are very rare. How is it possible that a butterfly can be active from July to late September and still present in excellent condition the following spring?

Intriguingly, Brimstones do self-care rather well. During the first few days after they hatch from the pupa, the butterfly is quite sedentary. It sits quietly in bushes or trees and does not draw attention to itself. It does not bask with its wings open but sits with leaf-like venated undersides on show, blending with ambient vegetation. In hot or cold summer weather, it takes to cover in foliage, concealed to great effect. On summer days when it is active, it is rarely out of cover before 11 am or after 4 pm, roosting early, sometimes before that that, reducing exposure time.

Brimstones are very good at not getting caught by the onset of bad weather. They are rarely seen away from sheltering trees, bushes, ivy, or dense sedge clumps, and react quickly to changes in weather. Brimstones can forecast rain, even when it is sunny, and will take cover in advance of rainfall (Adrian Hoskins, pers. com.). They know the difference between a cloudy spell and a lengthy period of overcast conditions; a feeding Brimstone will rest on vegetation during a cloudy spell and go to roost during persistent dull weather (Harding, 2021).

The butterfly’s general behaviour is quite conservative. While it can fly at a strong pace, it usually flutters from bloom to bloom in summer, avoiding the need for lengthy or conspicuous flights. It does not fling itself into tangled vegetation at any time of the year like some species do when mate-seeking or egg-laying.

The Brimstone cleans itself, using its legs to remove dust and debris from its head and thorax, and unhooks its proboscis to remove sticky pollen.

Despite these behavioral traits, a delicate insect is expected to show wear and tear after months of active living. Their generally good condition in early spring is a key reason why I do not believe the Brimstone spends several months in an active state before entering hibernation. While records show that the new generation of the Brimstone is active from July to late September or even early October, my transect records which extend over more than 10 years suggest that individuals are active for a few weeks and that most enter hibernation during the summer. The timing of over-wintering is likely dependent on when it hatched from the pupa and the weather.

Brimstone eggs are laid over several weeks, from late March to mid-June. Therefore, adult butterflies emerge from the pupa over an extended period. If a Brimstone hatched at the beginning of July it is probably in hibernation before the end of the month. If it hatches early in August it is likely to over-winter before the month is over. Prolonged bad weather during summer will see pupae lasting longer and adults resting in cover until conditions favour hatching from the pupa and feeding on flowers. If correct, this would explain why Brimstones are often seen during September, especially following a wet August. Finally, it makes no sense for a butterfly to expose itself to danger for months, especially when it is not in breeding condition.

Thus, perhaps there is no time during most Irish summers when one sees most Brimstones that reside in an area. However, in spring when all Brimstones are in the adult state there is a mass emergence from hibernation which in spring sees them concentrated in their often-discrete breeding grounds rather than dispersed across larger areas of flower-rich habitats. In the early stages of good spring weather, most of those seen are males but soon the females appear; the sexes are very active in spring, intent on finding mates and breeding plants. This behaviour makes counting large numbers easier, but the butterfly is not more abundant in spring than it was the previous summer before over-wintering.

However, the large concentration of these large, bright, characterful butterflies on bright sunny spring days is exhilarating after the drudgery of our muddy, damp, drab winter. The daffodil yellow males’ dash along the wood, hedge, and scrub edges brings vitality and pure joy to the nature lover, while the pale females delicate fluttering around buckthorns evoke living blossoms, their glowing leaf-like wings translucently petal-like in the crystal spring sunshine. Little wonder people see their first Brimstone as announcing the beginning of spring; little wonder English naturalist Matthew Oates called this mass emergence phenomenon, “National Brimstone Lift-off Day, the first truly warm day of the year”(Oates, In Pursuit of Butterflies, p. 220). It must be warm and sunny to tempt the Brimstone out in spring so when you see it, you know the weather offers the promise of happiness.

While the Brimstone offers the fascination of investigation, discovery, and ongoing inquiry, it offers much else besides, a view of a flower-rich countryside in the finest weather. The Brimstone is our ultimate sunshine butterfly, especially when back-sunlit wings are enjoyed. The male turns suddenly from matt yellow to gold in such light, inspiring for anyone, particularly for a photographer seeking to preserve the memory of a perfect experience, when the moment literally turns golden.

Look out for this moment in the weeks ahead…

References

Gutiérrez, D., & Wilson, R. J. (2014) Climate conditions and resource availability drive return elevational migrations in a single-brooded insect. Oecologia, 175(3), 861–873. doi:10.1007/s00442-014-2952-4

Harding, J. (2021) The Irish Butterfly Book. Privately published, Maynooth.

Learnaboutbutterflies.com

Nash, D., Boyd, T. and Hardiman, D. (2012) Ireland’s Butterflies a review. Dublin Naturalists’ Field Club, Dublin.

Nelson, B., and Thompson, R. (2006) The Butterflies and Moths of Northern Ireland. National Museums Northern Ireland, Belfast.

Oates, M. (2015) In Pursuit of Butterflies. Bloomsbury, New York.

Wiklund, C., Lindfors, V., & Forsberg, J. (1996) Early Male Emergence and Reproductive Phenology of the Adult Overwintering Butterfly Gonepteryx rhamni in Sweden. Oikos, 75(2), 227. doi:10.2307/3546246

Under the Wildlife Acts, hedgerow cutting is banned during the period March 1st to August 31st inclusive.

This ban is legally enforced, and many prosecutions have been taken by excellent National Parks and Wildlife conservation officers charged with protecting our diminishing heritage. Burning, cutting, and grubbing vegetation during this period is also prohibited.

If you see anyone breaching the law, take photos of the incident and machinery and contact your local National Parks and Wildlife Service officer. You can also contact the Gardaí.

The following are the contact details for the National Parks and Wildlife Service.

The Eastern region:

https://www.npws.ie/contact-us/eastern-division

Northern region:

https://www.npws.ie/contact-us/northern-division

Western region:

https://www.npws.ie/contact-us/western-division

Southern region:

https://www.npws.ie/contact-us/southern-division

Hedges are especially important for butterflies and moths. 65% of Irish butterflies use hedges. Some use hedgerow trees as breeding plants, some use grasses and flowers growing on the warm margins for breeding. In addition, many adult butterflies use hedges as territory, mating stations, nectar sources, flight paths, dispersal routes, and hibernation sites. The Brimstone butterfly uses hedgerows for all these reasons, while the Brown Hairstreak uses hedges for breeding, meeting and mating, feeding, and as a flight path.

A study by Merckx et al. (2012) found the hedgerow trees and extended width margins locally increased the number of larger moth species (also known as macro-moths) but not the abundance. Interestingly, they found that species richness and abundance were not affected by intensive farming, measured by the amount of arable land in the landscape. Both mobile and less mobile larger moths did better when extended width margins and hedgerow trees were present.

The benefits of trees in the hedgerow were especially strong for tree-feeding species. Increasing the density of hedgerow trees was recommended to lessen the effects of agricultural intensification. The study underlined the value of hedgerow trees, claiming “a disproportionate effect on ecosystem functioning given the small area occupied by any individual tree”.

The study also found a link between increased macro moth populations and ecosystem functioning (in other words, the higher moth abundance and species richness improve biological community functioning).

Why is this? Moths are associated with higher pollinator success, which benefits crops and animals, and moths are an important prey base for a range of species.

A study by Coulthard et al. (2016) showed that hedges are very important flight paths for moths. 68% of moths in the study were observed at 1m from the hedge and of these 69% were moving parallel to the hedge. Hedges are believed to provide the sheltered corridors needed by flying insects in our generally open, farmed landscapes.

These studies highlight how crucial hedgerows and hedgerow trees are for butterflies, moths, and biodiversity generally. It is crucial that hedges are protected and correctly managed. A badly managed hedgerow can be disastrous for some of our rarer species. For example, many species that breed on hedges lay eggs on the newest growth. Unfortunately, it is this outer part of the hedge that is removed by cutting. The Brown Hairstreak butterfly is extremely vulnerable for this reason, and Berwearts and Merckx (2010) report studies that found that annual mechanical cutting of hedges removes 80-99% of Brown Hairstreak eggs. A rotational cutting system that involves cutting one-third of the hedgerows in an area each winter resulted in the butterfly’s longer-term survival.

Even more serious is the removal of hedgerows by farmers who want to increase field sizes. Outside protected areas, this can be done between August 31st and March 1st. Given the importance of hedgerows to butterflies, moths, and many other species, our landscape cannot afford such losses. Another damaging though the smaller-scale practice is the replacement of hedgerows comprising several native species with a single species hedge, often non-natives such as Common Beech, laurel, and leylandii, among others. In some parts of the west, non-native fuchsia hedging has become naturalized, disfiguring the landscape, displacing native species, and reducing biodiversity. These alien species are of much less value because they have not co-evolved with the other species naturally present here.

Our hedges are crucial to our landscapes, giving our countryside character, building a sense of place, and hosting much biodiversity. The poet Wordsworth described the hedgerows at Tintern Abbey as “Little lines of sportive wood run wild”. While some management is necessary, a more relaxed attitude would be a great boost to butterflies and much else!

References

Coulthard, E., McCollin, D. & Littlemore, J. 2016, “The use of hedgerows as flight paths by moths in intensive farmland landscapes”, Journal of insect conservation, vol. 20, no. 2, pp. 345-350.

Merckx, T., Marini, L., Feber, R.E., Macdonald, D.W., Kleijn, D. & Sveriges lantbruksuniversitet 2012, “Hedgerow trees and extended-width field margins enhance macro-moth diversity: implications for management”, The Journal of applied ecology, vol. 49, no. 6, pp. 1396-1404.

Butterfly Conservation Ireland Annual Report 2022 is now available here:

Butterfly Conservation Ireland Annual Report 2022

We hope you enjoy it.